Many states within the USA and Canada have straight lines as a border, completely ignoring natural borders like mountains or rivers. Many American states and Canadian provinces are just rectangle-shaped, and a good half of the US/Canada border is made of two straight lines (one vertical and one horizontal).

Why was it decided to make it like this? I understand the colonizers made arbitrary decisions initially, by why didn't they pick more natural borders, for example following rivers and mountains?

  • 2
    No wars were fought with Britain/Canada after the War of 1812, at which point the far northwestern territories you are talking about weren't really settled. That's just wilderness across the northern border, so they just drew a line.
    – two sheds
    Apr 7, 2015 at 12:11
  • 6
    The borders align with latitude.
    – MCW
    Apr 7, 2015 at 12:43
  • 1
    youtube.com/watch?v=qMkYlIA7mgw this is a great video about this topic, explains everything nicely
    – Vajura
    Apr 8, 2015 at 7:46
  • There is a TV series "How States got their Shapes" with about 30 episodes that explains very nicely the history behind many of the surprising tidbits. Very often, the border isn't actually straight even when it seems to be, and conversely, sometimes the border is straight but leads to odd results (for instance, Point Roberts, WA, where a tiny tip of a peninsula is in the US, but the only way to get to the mainland is by boat, plane or through Canada). Apr 8, 2015 at 18:02
  • There is an issue with using rivers as borders - they can move. That is why little bits of Kentucky are across the Mississippi on the same side as Missouri. Arbitrary lines are at least a permanent solution when having a defensible position isn't an issue.
    – Oldcat
    Apr 8, 2015 at 21:01

5 Answers 5


Natural borders such as bodies of water prevailed where there were PEOPLE living around them. For instance, much of the eastern end of the U.S. Canadian border was defined by the Great Lakes and the St. Lawrence River. On the Maine-Canadian border, it was defined by forests used by Maine (or Canadian) loggers. In such instances, "strong fences make good neighbors."

When the "straight" borders (49th parallel and 141 W longitude) were defined, there were no (white) people living around them. "No one" (in a policy-making position) had any idea where the lakes, mountains or forests were. So people sitting in offices found it easier to negotiate straight lines as boundaries, and let the settlers find out what was on either side of them, instead of deciding where to put the "fences."

In the U.S., there are a lot of straight boundaries in western states that are sparsely populated, and have large chunks of desert or at least "deserted" land. E.g. Nevada, Utah, Wyoming, Colorado, the Dakotas. In the more densely populated eastern states, borders are more likely to be drawn along natural boundaries that separate groups of people.

The idea of setting out the western states in gridlike arrangements appears to have originated with Thomas Jefferson. By the time he became President, the states in the east (of the Mississippi River) had already had their shapes pretty much determined.

  • 1
    One effect of this is that it creates/exacerbates modern regional differences. For instance, the straight-line border between California and Nevada runs just a bit east of the crest of the Sierra Nevada, so people on the east side (especially in the Reno/Tahoe area) tend to identify much more with Nevada than California: they do major shopping in Reno, get news from Reno sources (at least prior to internet & satellite TV), often go to college there, &c. Life would have been much less complicated if the border had been set at the crest.
    – jamesqf
    Apr 8, 2015 at 18:51
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    @jamesqf: It sounds to me like those people have everything under control. What is so "complicated"? Apr 9, 2015 at 14:38
  • 6
    Concerning "no-one had any idea where the lakes, mountains or forests were": an example of this is the Treaty of Paris (1783), which originally called for the border between the British Empire and the USA to run due west from Lake of the Woods to the Mississippi River. This turns out to be impossible (the source of the Mississippi is well south of Lake of the Woods), and the border had to be renegotiated later on. Mar 13, 2017 at 17:47
  • the straight-line border between California and Nevada runs just a bit east of the crest of the Sierra Nevada "Just a bit east" in this case is equal to the entire width of the state of Rhode Island.
    – user2848
    Jun 15, 2020 at 19:06

States Borders

First off, most Canadian or American states' borders are not particularly straight. Even when they are supposed to be straight, there are often nooks and crannies.

But indeed there's a tendency to use simple straight borders when creating a territorial entity from scratch, especially on the basis of longitude and latitudes. We see this in many colonial borders, in America or elsewhere in the various European empires. Due to the way map are usually drawn, this often ends up looking like straight lines.

The advantages for doing so are obvious. Decision makers did not often have much details on local geographic features when portioning remote territorial claims into colonies. Even if they did, basing borders on geography was prone to create disputes. The inaccuracy of surveys aside, the natural twists and turns of geographic features, especially rivers (which to make matters worse may change course) are source of major headaches.

For instance, the recently settled long standing dispute between Maine and New Hampshire over islands in the Piscataqua River that forms their borders; Alabama and Georgia's dispute over their Chattahoochee River border; or Georgia and South Carolina's dispute at the Savannah River and its islands.

In contrast, there is only one 42nd parallel (incidentally part of the border between New York and Pennsylvania, which is fixed, simple, and objectively determinable.

Canadian-US Border

This border in particular seems straight because a huge 3,500 km section of the Canadian-US border was somewhat arbitrarily fixed at the 49th parallel. Most of the border west of the Lake of the Woods was first proposed in 1807, and decided in the Anglo-American Convention of 1818, with the Oregon section finalised in the Oregon Treaty.

The 49th parallel had formerly been proposed by Britain as a formal border with French Louisiana as early as the 1713 Treaty of Utrecht. This was revived after Louisiana was purchased as a satisfactory border for both. At the time Louisiana claims include the entirety of the Mississippi's western watershed, while Britain claimed the all of Hudson's Bay drainage basin. Both extended north and south of the 49th parallel, respectively. Setting the border this was, in an appealingly simple (on paper) straight line, was thus an acceptable compromise for both nations.

Most of Alaska's border with Canada was inherited from Russian times. It looks straight because most of it were fixed at the 141st meridian west under the Anglo-Russian Convention of 1825.

Multiple wars might eventually readjust the border to more natural terrain features. However, the reality is that the United States had not fought any war against Canada (or British North America) since the borders were demarcated. Consequently, the border remained as it was drawn when the land was largely devoid of European settlements.

Lastly, if you look closely at the border, there is nothing straight about the Canadian-US border east of the Lake of the Woods.

  • One thing that really surprised me when I looked into it was just how many freaking border disputes there were between US states. Even straight lines didn't always help. For instance the weird slanted lines a lot of states have tend to be due to historical incidents of incompetent surveying.
    – T.E.D.
    Apr 7, 2015 at 14:29
  • 16
    The border between the U.S. and Canada is both the longest undefended and longest-undefended border between two sovereign nations in recorded history. While the War of 1812 is sometimes considered to have ended in a stalemate, the outcome was probably better for both sides than victory would have been for either. Interestingly, the treaty between the U.S. and Canada explicitly provides that either side may legitimately dissolve it with thirty days' notice; I wonder if the existence of provisions to dissolve a treaty helps prevent either side from giving the other cause to do so.
    – supercat
    Apr 7, 2015 at 15:19
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    For a nice account of the weirder bits of the US/Canada border see cgpgrey.com/blog/…
    – Alan Munn
    Apr 7, 2015 at 16:39
  • Of course, it was meant to be the 49th parallel (or so) only until the Mississippi, at which point it would have (as far as I can tell) turned south and looped back (Territory west of the MS was acquired later as the Louisiana Purchase). Unfortunately, the Mississippi does not, in fact, reach the 49th parallel.
    – Random832
    Apr 8, 2015 at 3:54
  • @Random832 What do you mean? The 49th parallel border postdates the Louisiana Purchase by 15 years.
    – Semaphore
    Apr 8, 2015 at 5:31

The only place you really have the large straight-line International border is West of the Great Lakes (up until Vancouver)1. Probably the most succinct reason it was made that way, rather than at natural boundaries like everywhere else, was that neither side actually had any citizens settled in that area yet.

Originally (post-Louisiana Purchase), the USA claimed the entire Mississippi(/Missouri) watershed, while Britain claimed the Hudson Bay watershed. However defining an exact watershed was no simple matter, particularly when native nations controlled most of the headwater areas.

So after the War of 1812, the USA and the British agreed to simplify the border on the west side of the Great Lakes at the 49th parallel. Again, native nations still controlled most of this area. The borders to the East where both sides had cities remained at more natural boundaries.

For the US states, generally borders tended to get set up while the areas were still territories (mostly uninhabited by American Citizens), so cultural communication/travel barriers weren't as much of a consideration. Additionally, there was a feeling in the US Congress that all new US states should be roughly the same size, which led to a lot of territories having relatively arbitrary lines drawn through them to make properly-sized states. Slavery also ended up having a hand in a surprising number of state border placements (for example, its almost solely responsible for Oklahoma's weird "pot" shape, made up of mostly straight lines.)

If you are generally interested in US borders, a good book to pick up is How the States Got Their Shapes. There was also a series by that name produced for The History Channel. You might be able to find some of it from your favorite streaming TV sources.

Canada I don't know as much about, but its pretty clear that their even sparser population led to them not caring as much about keeping the physical size of their provinces down.

1 - Yes, there's a tiny straight bit on the northern border of Vermont too

  • 1
    I believe the other long straight line he had in mind was the East edge of Alaska: some 644 miles. While far smaller than the ~1,270 mile border South of Canada, it's still quite relevant. Apr 7, 2015 at 16:43
  • 1
    Even the original colonies were mainly arbitrary lines set up while the areas were mostly uninhabited: the colony grants tended to be of the form "from 31 degrees north to 36 degrees north", or "along river X to its northernmost point, and from there west to the Pacific Ocean".
    – Mark
    Apr 7, 2015 at 22:29
  • @Mark - The weird semicircle at the top of Delaware is another example of this. The state's northern border was defined as exactly 12 miles from a specific building in a specific settlement near the coast.
    – T.E.D.
    Apr 7, 2015 at 23:01
  • Another river problem Rio Grande border disputes Apr 8, 2015 at 1:09
  • 1
    Note that about half of the US-Mexico border is also made up of several straight lines.
    – jamesqf
    Apr 8, 2015 at 18:57

The shape of borders reflects the history and commerce at the time. In the eastern US, borders are often formed by geographic features because transportation at the time was very relevant - and transportation largely depended on waterways. For instance, the northern border of Indiana is straight - but it's about 10 miles further north than it would be as an extension of the Ohio border. This was made to give Indiana access to Lake Michigan.

The western border of Massachusetts is straight except for the southernmost few miles. This happened because of a mountain range. This little notch would have been almost impossible to police from MA, but is easy to reach from New York.

Going further west, there are several factors that led to straighter borders.

  • As others pointed out, less white population.

  • Less was even known about the geography of those regions, especially pre-Lewis&Clark. A few of the borders are quite old. For example, the northern border of Tennessee/Kentucky/Arkansas/Oklahoma/New Mexico/Arizona - it was shifted north a little starting in Oklahoma. Another example are the borders between New York and Pennsylvania, and between PA and Maryland/West Virginia. Those borders were originally intended to extend all the way through the Continent.

  • Much of the Midwest has far fewer natural features that would lend themselves as border. There's the Mississippi river, of course, but not much going west from there until you get to the Rockies.

  • When those borders were set, transportation depended on railroads more than rivers. Access to navigable waterways was far less important than in areas settled earlier.

  • A lot of the economy in the western US depended on resources such as gold, silver, later also oil etc. These resources generally don't have perfectly known boundaries. Straight lines would come about either to protect the resource and a buffer around it, or conversely, when a several groups claimed the same resource, and it had to be split.

  • Some boundaries in the West still are determined by rivers, for instance the Colorado between Arizona/Nevada and California, or the Columbia between Washington and Oregon.

  • I believe the border of Wyoming had something to do with Yellowstone, although I don't recall the exact connection.


CGP Grey has a video about this nice border between Canada and the USA, and how it isn't that straight as you think.


edit: In this video Grey explains why the border between Canada and the US is supposed to be straight, why it isn't and some rather odd analogies.

  • Very cool, the other videos in his channel is extremely interesting too ! I just learned a lot of things :)
    – Bregalad
    Apr 9, 2015 at 20:42
  • 1
    @Bregalad ikr, CGP Grey is one of my favourite youtubers. I really enjoyed watching "The difference between Holland, the Netherlands & a whole lot more" and the vids about the vatican Apr 10, 2015 at 22:09

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