I've always been a bit fascinated by maps. When I was a kid, we had placemats with a historical/cultural map of the Chesapeake Bay, and being the "read anything in front of me" child that I was this may have been formative. I remember having a world political map on the wall, and later a world topographic map (including the sea floor) on my ceiling. I always loved looking at the maps of fantasy realms like Middle Earth and Earthsea that would show up in the front of books. (Yes, I am geek.) When I started driving, back in the days before GPS and smartphones, I had a good collection of ADC street atlases floating around the car.
Along with that, I've also found the idea of geopolitical boundaries to be ponder-producing. I grew up about a quarter of a mile from the Baltimore City/Baltimore County line, and it amazed me that when crossing from one side of the parking lot of Cedonia Mall, or leaving my grandparent's back yard to play in the small patch of woods behind, I was crossing into an area subject to different laws enforced by different police forces. There was no line on the ground or anything, we didn't even cross a stream or a hill, yet somehow people were supposed to agree that This Land Is Different. (I've even crossed the U.S.-Mexico border on foot, and noticed nothing different on either side.)
So I was delighted to stumble upon this piece at BigThink about a peculiar area of the U.S.-Canada border, part of a series on strange maps. A long straight stretch of the border follows the 49th parallel (at least, in theory -- the 19th century survey markers are often hundreds of feet off, raising the question of whether the actually boundary is where is the markers or the theoretical line). At the eastern end of that stretch, at Lake of the Woods in Minnesota, the border bends due north to the "Northwest Angle", an artifact of a faulty map used in treaty negotiations.
The land, however, did not read the map, and insists on projecting itself across the line in a few places. How many? Well, that's not clear...different maps show the swampy coastline differently. A fine example of how the map is not the territory.
Check out also this map of "waterflow toponyms" -- i.e., the use of terms such as "brook", "run", "stream", etcetera in naming small flowing bodies of water. "Run" and "branch" predominate in Maryland, which matches my experience.