Missouri River, South Dakota's Great Divide

"What does the Missouri mean to you?" I was asked.

South Dakota is one of those roughly rectangular states in the heartland of the USA. The Missouri River runs through it north to south, dividing it into two nearly equal but very different halves. To the west landscapes are mostly rugged and sparsely vegetated. To the east they're subdued and covered in plants. So after pondering the sign's question, I decided that was what the Missouri meant to me—South Dakota's Great Divide.