And why did it never—as I understand—take off the way its early promoters thought it would, being at a strategically important and commercially advantageous spot at the confluence of the Ohio and the Mississippi?
I’ve driven through a handful of times over the years and heard all the stories—about the flooding, the railroad bypassing the city, the corruption, the racism and resulting violence, etc. But I grew up in a Midwestern river city that’s had its fair share of similar challenges over the past couple of centuries, and I’ve visited many others, and I don’t know if I’ve ever been anywhere that feels as hollowed-out and bleak as Cairo.
Anybody with more to say should feel free, but previous answers point toward the factors you've mentioned with some interesting detail:
https://www.reddit.com/r/AskReddit/comments/eddwx/what_the_hell_happened_to_cairo_illinois/c179xvu/
https://www.reddit.com/r/AskHistorians/comments/5ym75d/what_happened_to_cairo_illinois/