re: What is the greatest Southern United States river?

There is a point just outside my hometown of Olney, Texas, where if a rain drop were to hit precisely on it, 1/3 of the water would go to the Gulf through the Mississippi, 1/3 through the Trinity, and 1/3 through the Brazos. It's just kind of a gradual slope, but you can see a pretty long way from what seems like a rather ordinary patch of prairie.