“The junction of the Mississippi and the Ohio was a confluence of thick machine oil and rosewater. The two looked so different that it was hard to believe they could fuse into a single element without curdling. The Mississippi held the foreground and the Missouri shore; the Ohio had Kentucky. The clean pencil stroke between the brown and the pink, running due west to east for more than two miles, must have been the one place in the United States where the cleavage of the Mason-Dixon line had its exact counterpart in nature.”