I've crossed the Continental not once, not twice, but about eight times this year and it occurred to me today -- a delayed lightbulb -- that I had no idea what the heck it is. OH heavens Betsy. HELLO, GOOGLE!
Also called the "Great Divide," it's a natural boundary line that separates water that flows into the Atlantic, Gulf of Mexico and Pacific. It's a north-south line that runs from Alaska to South America. In the Lower 48, it follows the Rockies.