Continental Divide

Let's say two raindrops fall on Colorado, one inch apart. Say one raindrop falls to the East of a particular ridge, and the other drop falls on the West of it. Now say that the Eastern drop flows down a mountain, into a stream, to a river, to a bay that feeds into the Atlantic. The Western drop, let's say, flows the other direction, into different streams, rivers and bays that lead it to the Pacific. That ridge then, would be the Continental Divide. 

How geographers determined the exact ripple of North America that constitutes it, I'll never know. What I do know is that it weaves down the center of Colorado, and that no matter which side of it a raindrop may fall, that little guy has a scenic journey ahead.