I realized writing this how much I obsess on rivers / bodies of water -- when you are cycling, you always observe the fall lines -- following those lines -- you are probably taking the path of least resistance, which is why rail lines so frequently follow rivers. And why cyclists follow rail lines!
1214 miles down -- 2286 to go! Over one-third done! Finished today (virtually) crossing into Texas! Still 5 or 6 weeks of riding to complete, but let's hope the better weather holds!