From Cape Girardeau,Poplar Bluff, (5-6)
These two well-known towns in the Mississippi river valley were characterized by widespread poverty back in the day, especially when it came to their black citizens.
Comes flivverin' in, (9)
Flivverin's not just a cool word. It also tells us that these people aren't cruising in in fancy Cadillacs. They drive jalopies.
Or ridin' mules, (10)
Back in the day, mules were owned by those who couldn't spring for a horse, so in a poem like this, it's a sure sign of a lack of cash.