Generally, most people think of the United States as a single mass of land. Of course there are a plethora of lakes, rivers, and mountains separating the various states; however, despite these divides, we see this portion of North America as a land united. Yet, this isn't entirely accurate.
In the Tenton Wilderness of Wyoming there is a creek that disrupts the united vision of the United States by dividing the country in two. That's correct: the US is divided into two parts by a single water line. This means that, if I fish wanted to swim from the Atlantic Ocean to the Pacific, it would be able to do so (theoretically, of course, it would probably get eaten by a bear mid trip). Ultimately, at a specific dividing point, a drop of rain has a 50/50 chance of landing and flowing out to the Pacific or down to the Gulf of Mexico, which connects to the Atlantic Ocean.
The dividing point is called the "Parting of the Waters Natural Landmark." Here, the Two Ocean Creek flows down from a plateau in the North until it reaches a point called "Two Ocean Pass" (pictured below). At this pass, the creek splits in two, forming what it known as the Atlantic Creek and Pacific Creek.
If you stand in the center of this divide, one foot will be linked to the Pacific ocean and one foot will be linked to the Atlantic. It's kind of neat to think about, and somewhat akin to standing on either side of the prime meridian (which divides the Eastern and Western portions of the globe). In the Eastern portion of the creek, the water follows the Atlantic Creek and flows for more than 3,480 miles (5,610 km) to the Atlantic Ocean (via the Yellowstone, Missouri, and Mississippi Rivers.) To the West, the water leads to the Pacific Ocean after some 1,35 miles (2,170 km). The Pacific Creek travels via the Snake and Columbia Rivers.
Of course, it should be noted that North America is not actually divided. At least, not geologically speaking. Still, I think that the Parting of the Waters is a good reminder that things are often far more complex than they initially seem.