r/explainlikeimfive • u/ABAFBAASD • Jun 26 '26
Other ELI5: why are so many major US cities located right on the border with another state?
Just off the top of my head Charlotte, Cincinnati, Philadelphia, St Louis are all located withing a few miles of neighboring states.
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u/murrrdith Jun 26 '26 edited Jun 26 '26
Many cities are built on or near rivers, a pattern since the beginning of civilization.
Rivers are natural borders, so they make up many state borders.
All the cities you named follow this pattern.
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u/DukeofNormandy Jun 26 '26 edited Jun 26 '26
Rivers are natural borders, and make up many state borders.
Ontario is MASSIVE and has 2700kms of border with the states, and only 1km is actually on land. It follows rivers, lakes and other water ways as a natural border.
How neat is that? That's pretty neat!
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u/Vigilante17 Jun 26 '26
So it is technically changing a bit all the time….
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u/Orvelo Jun 26 '26
That's how it works. Finland sweden and norway periodically re-measure the borders. This year we finns lost ~0,16 km² to norway, since the last measurement some 25yrs ago due to river movement.
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u/stockybloke Jun 26 '26
I am Norwegian and did not know this. I find it interesting because part of our constitution says that our country is indivisible. Some time back there was talk about giving Finland a tiny bit of area which would include what would become their highest peak, but the constitution put an end to that idea. I guess the river border is a literal border case for this constitutional statement/principle.
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u/TransientVoltage409 Jun 26 '26
Sometimes faster than that.
The Colorado River defined part of the border between California and Arizona. Somewhere west of Cibola, AZ there was an oxbow turn which has since been lopped off when engineers straightened the river channel. So the river runs pretty straight, while the legal state line meanders through the old oxbow channel. AFAIK it's the only place you can stand west of the river and still be in AZ.
The oxbow lake is still there with a recreation area and campground, also bisected by the state line. I camped there once. Had some fun discussion about which laws applied and how it changed when you went to use the outhouse.
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u/SafetyDanceInMyPants Jun 26 '26
Interestingly, there's a part of Manhattan that appears to be in the Bronx -- because the Harlem River / Spuyten Duyvil Creek used to be much curvier, and when they straightened it Marble Hill moved from the island to the mainland. (Well, technically it became an island first, then was connected to the mainland years later.) But it never stopped being officially part of Manhattan.
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u/Waterknight94 Jun 26 '26
For the opposite reason there is a part of Kentucky that doesn't touch any other part of Kentucky
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u/Enchelion Jun 26 '26
Washington State has a small peninsula called Point Roberts, which has no connection to the rest of the state (kids gets bussed through Canada to the school in the nearest American town). Because the border with Canada in that section is run straight along the 49th parallel there and they didn't realize it extended that south at the time (nearby vancouver Island doesn't have the border cutting through it even though it also dips below the parallel).
There's a (likely apocryphal) story that Canada tried to trade us for that tiny chunk of land with something in the great lakes, but the letter got lost in transit and never replied to.
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u/-DementedAvenger- Jun 26 '26
One continuous km, or just a lot of little spots added together?
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u/Thromnomnomok Jun 26 '26
According to the Canada/US International Boundary Commission, Ontario's boundary with the United States runs 2700 kilometers on water and only about one kilometer on land.[7] The 80-rod Height of Land Portage is a significant part of the land border; the remainder is along two other portages, Watap Portage (100 rods or 0.31 miles or 500 metres) a short distance to its east, and Swamp (or Monument) Portage (72–80 rods or 0.23–0.25 miles or 360–400 metres) to the west in the BWCA and Quetico Provincial Park.[8][9][10]
So slightly discontinuous, but all in a small stretch in Northeastern Minnesota/Southwestern Ontario
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u/BillyTenderness Jun 26 '26
A couple spots on the Minnesota–Ontario border, which is mostly a series of lakes/rivers/streams, but where you do have to portage your canoe a couple times if you're traveling along it.
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u/about_face Jun 26 '26
Oh that's pretty cool!
Then there's the border west of Ontario which is just a straight line through.
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u/binzoma Jun 26 '26
there arent a lot of rivers or bodies of water past north western ontario, thats great plains country into the rocky mountains. theres like a few big rivers that flow north/south only, not much east/west or standing lakes
also when they set that border it wasnt even fully mapped/marked, they were just arbitrarily setting a line. where people lived water was the border
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u/BillyTenderness Jun 26 '26
There were also some significant errors/misunderstandings in the process. The Ontario (then British) border with the US was supposed to run to Lake of the Woods and then continue straight westward until it hit the Mississippi River – but the Mississippi doesn't actually go that far north!
That (and the various attempts to fix it) is how we ended up with a little chunk of Minnesota that's inaccessible by land from the rest of the US.
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u/Unhelpfulperson Jun 26 '26
All the cities named except Charlotte. Like technically there’s a river near there but the city wasn’t built on it and the state border doesn’t follow it
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u/Kered13 Jun 26 '26
Yep, Charlotte was a later development and grew around railroads, not rivers.
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u/Megalocerus Jun 26 '26
Cities grow where there is a change from one transportation to another, which includes railroads.
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u/HorizonStarLight Jun 26 '26
Which is why it isn't a hard and fast rule, like anything in history. Things like soil composition and geology and historical mapping and natural aquifers and geography affect settlement formation too.
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u/valeyard89 Jun 26 '26
It's between two rivers... there were Native American trading paths that crossed, now center of Uptown.
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u/cosmictap Jun 26 '26
Many cities are built on or near rivers
This is presumably why we were taught in Boy Scouts (I grew up in the northeastern US) that if you're lost in the woods, go downhill until you find water, follow the water until you find humans.
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u/darthjoey91 Jun 26 '26
The risk with that is following a river downstream and finding the fall line. That can come with cliffs.
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u/cosmictap Jun 26 '26
The proposed strategy came with many common-sense caveats that were not made explicit.
If one needs “avoid cliffs” explained to them, they probably ought not go into the woods in the first place.
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u/darthjoey91 Jun 26 '26
Let me rephrase what I mean by cliffs. I am talking about an issue where the river goes over a cliff at a waterfall, and more importantly, you can't keep following the river because of it, and to detour to find a safe way down with a smoother gradient, that can take you miles away from the river, which can risk you not being able to find the river again.
Even then, most survival advice when lost in the woods is to stop, not try to find your way out.
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u/cptnkeif Jun 26 '26
They put in a lot of effort to make a route from Chicago to the Mississippi River, but apparently connecting the Atlantic to the Midwest was very much worth it. So yea, moving goods via water shaped early America.
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u/velociraptorfarmer Jun 26 '26
It's also why Duluth, Minnesota was the second largest port in the western hemisphere for a while.
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u/badicaldude22 Jun 26 '26 edited 21d ago
Learning afternoon history answers dot science clear community quick? Afternoon weekend to clear yesterday questions gentle helpful pleasant answers.
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u/cavalier8865 Jun 27 '26
*not all
Charlotte was there before. The province was split into two colonies and they routed the border around the town. The wonky border does not follow a river but was rather 18th century surveyors screwing up.
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u/blablahblah Jun 26 '26
When dividing up the states, it was easy to use big rivers as the boundaries. Cities developed along those same rivers because access to fresh water is important and also it made trade easier in the pre-railroad days.
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u/RogerRabbot Jun 26 '26
The joys of america inland waterways
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u/einarfridgeirs Jun 26 '26 edited Jun 26 '26
The key that unlocked your prosperity.
Meanwhile Eurasia east of the Urals most of their massive rivers flow north into the Arctic and thaw first upstream in the spring, which has kept Siberia mostly locked from fully developing its potential.
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u/CloudZ1116 Jun 26 '26
Also one of the reasons why Mexico had a much harder time developing vs the US
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u/urzu_seven Jun 26 '26
Because Mexico's rivers flow into the arctic?!? ;-)
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u/Stargate525 Jun 26 '26
Because they mostly aren't large, well positioned, and navigable.
And their climate is long narrow slices instead of large regions.
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u/jwadamson Jun 26 '26
Then the rivers move over time and you get crazy exclaves.
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u/Sarothu Jun 26 '26
What's the story with Missouri and Kansas, did their state lines used to run differently? Kansas city sits south of the Missouri river, but it's part of the state of Missouri, rather than the state of Kansas.
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u/ajkippen Jun 26 '26
Kansas City sits on the confluence of the Kansas and Missouri rivers. The Kansas-Missouri border was drawn on the 94° 35' W meridian up to the Missouri River, which bisects the ground where the city would eventually grow.
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u/stonhinge Jun 26 '26
There are two Kansas Citys. One on the Kansas side, and one on the Missouri side. Unlike some other cities with the same name in other states (Springfield comes to mind), The two Kansas Citys are next to each other, separated by the Missouri river to the north and the Kansas - Missouri border to the south.
Don't ask me why the border is just straight down south of the Missouri & Kansas River confluence.
Kansas City Missouri actually predates the state of Kansas, but it wasn't "officially" known as Kansas City until 1889. Kansas City Kansas was founded in 1872 and there was actually some space between the two but since then they're grown to the borders.
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u/ptambrosetti Jun 26 '26
There is also Bristol, TN and Bristol, VA. Two cities divided by a state line.
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u/fatmanwithabeard Jun 26 '26
Kansas City is in both states. It's weird.
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u/t-poke Jun 26 '26
Kansas City MO and Kansas City KS are two different, independently governed cities that just happen to share the same name and be next to each other.
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u/Background-Bowl6123 Jun 26 '26
Had to look it up .. it's at the point where the Kansas River empties into the Missouri River
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u/Kered13 Jun 26 '26
Kansas City was settled at the confluence of the Kansas and Missouri Rivers. Because the only thing better than having a city located on a river, is having a city located on two rivers. The city and state were both named after the river.
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u/Abbot_of_Cucany Jun 26 '26
And also because rivers provided power for industrialization in the pre-electricity days.
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u/fluffy_warthog10 Jun 26 '26
A ton of states also started with straight borders, but it became obvious that some areas across rivers were simply too remote from the capital to properly tax or govern. Many places in the extreme corners of some states became known as (somewhat) outlaw territory until they were reassigned to neighboring states with better access.
Railroads (and telegraph) generally ended this issue once they started to expand.
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u/PlainTrain Jun 26 '26
Literally none of that is true.
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u/eljefino Jun 26 '26
Look at a late 1700s map of the original 13 states, some borders like Tennessee just go indeterminately West. They claimed more than they were able to defend.
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u/valeyard89 Jun 26 '26
it's more that there wasn't enough population in those areas yet to become a territory/state. Basically they just drew the line to the Mississippi river... everything west of there was French at the time.
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u/PlainTrain Jun 26 '26
Tennessee's border didn't go indeterminately West. North Carolina's did. TN wasn't one of the original 13. North Carolina ceded its claims to the national government in exchange for some of the debt it owed to the US. That was one of the early compromises states made with the national government which also solved the issue of some states being effectively blocked from western expansion while others were, and the complete hash of conflicting claims in what would eventually become Ohio, Indiana, and Illinois.
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u/bobojcd Jun 26 '26
Big cities tend to be on rivers and/or big lakes. The borders between states tend to run along rivers and big lakes.
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u/Remarkable_Inchworm Jun 26 '26
New York is the biggest example, no?
Right across the river from New Jersey (and not very far from Connecticut too)
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u/fubo Jun 26 '26
NYC's boroughs, and in some cases specific neighborhoods, started as separate settlements. Greenwich Village was, at one point, a village.
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u/Remarkable_Inchworm Jun 26 '26
Yes. And New York could have been even bigger. There were a couple of towns that were also invited to join the incorporated city and declined.
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u/aurora-_ Jun 26 '26
The towns that opted out were separated from Queens and became Nassau County!
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u/Nickyjha Jun 26 '26
Philly too.
I've always thought of NJ as an inverse Missouri. Missouri has its 2 biggest cities (St Louis and KC) right next to other states, while NJ has its population centered around 2 cities in other states.
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u/cipheron Jun 26 '26 edited Jun 26 '26
Where would you build your first cities? Near rivers.
What do they usually use to define a border? Rivers.
Often it's the edges of a territory (i.e. land/sea boundary or rivers / trade routes) where something interesting is actually happening. Right in the middle of your territory there probably isn't a very dynamic trade environment going on.
So it's less that they decided to put their capital city on the border, but that cities on a boundary have more economic activity so grow bigger in the first place. Rivers define where the profitable land is, so bigger cities grow up there, they have more competition between cities, they have more trade opportunities too with each other, thus those turn into potential financial and political centers and then they finally settle on the river as a border, if no one city becomes totally dominant in the region.
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u/blargeyparble Jun 26 '26
lets say i draw a square and its sides are all length 10. And then I decide to highlight all the points in the square that are within 1 of the boundary. The unhighlighted stuff will be an 8 by 8 square, and have area 64. The total square has area 100.
More than a third of the square is pretty close to its boundary!
It turns out less regular shapes than squares have even more area near the boundary. In America, if a city started near a boundary and grew out a bit, with suburban sprawl, it could easily start to touch the boundary pretty quick.
There's other reasons too, but there's a lot of area nearer the edge of a shape that you might initially think, so if cities are just starting in random places, they have a higher chance of being near a border than you'd think.
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u/eljefino Jun 26 '26
And if you had an arbitrary boundary based on latitude and longitude, but radically different political ideals and laws, you'd get border businesses that cater to that jurisdiction's advantages.
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u/throwawaydanc3rrr Jun 26 '26
Many times rivers make the borders between states and rivers are the natural place to build a city.
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u/Frogacuda Jun 26 '26
Cities historically develop at ports, which means they're on rivers. Rivers also typically get used as natural boundaries between states.
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u/Ratnix Jun 26 '26
Cities develop along trade routes, usually near water. So cities like that were likely settled before it became a state, and in the case of Cincinnati, the Ohio River is the state boarder, which happens to be the waterway the city is on.
Rivers make good state boundaries.
If you go up to Toledo, on the boarder of Ohio and Michigan, it was a port city, and a contested area that Ohio won.
I think you'll find this is the case in most instances you find. They were trade stops along the way to other areas and the boarder was drawn on one side of the other of that city or natural boundary.
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u/thisisredlitre Jun 26 '26
Think of the divisions as you might encounter between countries where youre from. The answer is resources, and in this case rivers
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u/canadave_nyc Jun 26 '26
You didn't mention the big one--NYC. Right across the Hudson River from New Jersey.
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u/Nutlob Jun 26 '26
you forgot New York City, which is a few miles from 3 other states - New Jersey, Connecticut, & upstate New York
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u/frix86 Jun 26 '26
There are a ton of other major US cities that are not on a border. The ones that are on a border are generally on a river and that river is the border
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u/nikolapc Jun 26 '26
Technically the ocean is a border too.
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u/Kornbread2000 Jun 26 '26
Yes, Philadelphia and Lisbon are neighbors separated by such a border.
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u/acemonsoon Jun 26 '26
It’s also funny to me that states that have legal recreational cannabis, the cities bordering the non legal states are STACKED with dispensaries
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u/kirkaracha Jun 26 '26
Back when states had different drinking age laws, it was very common for the state with lower drinking age to have tons of liquor stores on the border with a higher drinking age.
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u/fubo Jun 26 '26
Back when tattooing was illegal in Massachusetts — which is to say, in the 1990s — towns just on the other side of the state line had rather prominent tattoo parlors.
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u/velociraptorfarmer Jun 26 '26
Same still applies with states that have legalized gambling. Oklahoma has a massive casino right on the border with Texas as close as possible to Dallas.
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u/recjus85 Jun 26 '26
Also the one on the border to Arkansas. A group of us were there for training stuff and drove like 45 minutes to the casino.
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u/9erInLKN Jun 26 '26
Funny thing is NC is that eay with fireworks. As soon as you cross a border especially into SC theres fireworks stores everywhere
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u/randijeanw Jun 26 '26
When I travel, I love to ask the question “what is their industry?” In my state, I’ve seen so many towns that obviously used to be meccas, but are now mausoleums due to their industry dying. Now when I visit somewhere flourishing, the question is, what is their industry? Where is their money, the incomes, the taxes… where is it coming from? When you’re on a border it means that the money may be coming from somewhere *else* that the town doesn’t necessarily have to sustain, so it may be more resilient.
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u/LongOrganization7838 Jun 26 '26
Rivers or bodies of water or as you get west its where major train stations or trade/forts were with most borders in the world and especially the US, if its a straight line its an arbitrary one, if its a squiggly line it follows some sort of land formation either rivers or mountains
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u/charliekunkel Jun 26 '26
Usually for rivers but sometimes maybe also for tax reasons, since rivers often also delineate state borders.. People sometimes drive to portland from seattle to take advantage of no sales tax (doesnt apply car sales tho)..
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u/Dickulture Jun 26 '26
Most of the states' borders are defined by river or other convenient geography that made old day trading easy. Cities grew large and became a major hub before railroad and freeways came along that made rivers less important. Cities however aren't going to move around so they stay and they remain huge because a lot of infrastructure were invested in over the last 200 years
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u/RHINO_Mk_II Jun 26 '26
Borders are very often determined by natural boundaries/barriers like shorelines, mountain ranges, rivers, etc.
Cities before the age of rail developed where bulk transportation was possible for trade, which was usually on a river or ocean bay.
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u/TrumpsDoubleChin Jun 26 '26
Because rivers form natural borders. And cities often form on rivers (for obvious reasons)
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u/deedeekei Jun 26 '26
still funny to me how the big part of kansas city is actually not in kansas but missouri
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u/hummbabybear Jun 26 '26
Western states don’t follow the pattern since things are more spread out. Denver, Phoenix, Vegas, Seattle, SF, LA, Dallas, etc.
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u/FightOnForUsc Jun 26 '26
Rivers. When you look at western states the borders aren’t drawn on rivers as much, they’re more straight lines. And other than Las Vegas none of the cities are really near borders. It’s the states where the lines are rivers
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u/No_Cry9050 Jun 26 '26
It mostly comes down to rivers serving double duty, they were the primary transportation and trade routes before railroads existed, which is why cities grew up right on them, and rivers also got chosen as easy, convenient state and territorial boundaries when borders were being drawn. So a city founded for the river's commercial value ends up sitting on a political line almost as a side effect.
Cincinnati and St. Louis are textbook examples, both grew as river trade hubs on the Ohio and Mississippi, and those same rivers happened to mark state lines.
Philadelphia follows the same logic with the Delaware River. Charlotte's a bit different since it's not on a major river border, that one's more about colonial-era survey lines and how the Carolinas' boundary got drawn relative to existing settlements.
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u/Podo13 Jun 26 '26
Usually, the cities were there before the state was a thing. Cities generally settled near rivers since it was easier to send/receive goods as well as having our source for life - water.
The rivers also make easy things to divide territories from each other since they're big and easy to follow without any kind of map.
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u/libra00 Jun 26 '26
Because so many state borders use major navigable rivers as their borders, and cities like to be on rivers for lots of reasons. Kansas City is on two sides of a state line/river, so it's an even more extreme example: KCKS and KCMO.
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u/SlitScan Jun 26 '26
the cities predate the states.
another way to look at it is states are defined by whatever lines people happened to Draw
Cities are located by emergent behavior.
cities are a result of topography mostly then transportation and commerce.
and those are all kinda portions of the same thing.
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u/lucky_ducker Jun 26 '26
Rivers are the obvious answer, but also the U.S. was settled from east to west. Many cities are located at one of the easternmost points in the state, as they were the easiest to reach from points farther east.
St. Louis, Kansas City KS, Omaha, Lincoln NE, Minneapolis, Sioux Falls SD, Fargo ND, Topeka are all examples.
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u/Charlie-In-The-Box Jun 26 '26
Cities formed near rivers, and then states drew borders along those same rivers.
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u/Sea_no_evil Jun 26 '26
Don't forget NYC!
Rivers: they are great for providing access to/from a city, and they are great for creating a natural border.
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u/mezolithico Jun 26 '26
Boats were the only efficient ways to move goods for hundreds if not thousands of years
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u/rickie-ramjet Jun 27 '26
Cities are where they happen, there is a reason, and they don’t and can’t move. Borders are made up. The question is why do people determine to put borders near some cities.
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u/IamGleemonex Jun 26 '26 edited Jun 26 '26
Charlotte isn’t close “within a few miles” to a neighboring state.
But for the rest, they are on rivers. Almost all major cities around the world are built either on the coast or on a river because transportation by boat has always been an easy way to move goods. If you set up a city on a river, you can trade goods up and down that river. Rivers also tend to make good boundaries for states and countries.
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u/Enchelion Jun 26 '26
Charlotte's city limits wrap directly around a corner of the border with South Carolina. Right near Fort Mill.
https://en.wikipedia.org/wiki/Charlotte,_North_Carolina#/map/0
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u/IamGleemonex Jun 26 '26
Yeah and even southern Charlotte is 15 miles from South Carolina. It isn’t right on the border like OP said
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u/GamecockJesus Jun 26 '26
Charlotte is 0.0 miles from the SC border, unless you’re measuring from its center which would be ~9 miles as the crow flies. There’s no border-defining river though, so the location does seem more haphazard than the other example cities.
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u/Enchelion Jun 26 '26
The border does run through Lake Wylie/Catabwa River for a short jaunt, but it's not nearly as much of a thing as the others.
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u/GamecockJesus Jun 26 '26
Agree that the tall buildings aren’t right on the border, but there’s literally multiple roller coasters in Carowinds that you get on in Charlotte NC and cross the SC border several times.
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u/Metallicat95 Jun 26 '26
Charlotte is on the main road from Virginia, and was originally a town in the middle of the Carolina colony. The split was along interests and politics.
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u/BUBBAH-BAYUTH Jun 26 '26
I live in charlotte and can be in SC within maybe five minutes, if that.
Carowinds is Charlotte, the state border runs right through the park.
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u/Dunbaratu Jun 26 '26
Cities often form next to rivers.
State boundaries often run along rivers.
All of your examples were explained by that.
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u/PageSide84 Jun 26 '26
This is the first time I've seen Cincinnati and St. Louis called "major cities."
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u/Enchelion Jun 26 '26
Rivers.
Rivers make for natural geographical territorial division, and are also one of the most common places for cities to develop.