I just re-read your post after initially replying having missed the important detail that the now-private parts are the plots originally granted to the railroad

I just re-read your post after initially replying having missed the important detail that the now-private parts are the plots originally granted to the railroads. My last reply here was made without grasping that. Are these "rail line" situations the only (or at least vast majority of) places where these public/private checkerboards exist? Or did the government actually sell other land in such a pattern at the request of the buyer?