Around the late 1800s, farmers had to take a gamble to try and get by. The gamble was getting loans from banks for the farming supplies they would need for the year hoping that their crops would do good enough to repay the banks, farmers were always poor and didn't have enough cash to get the supplies straight up. It was their only choice and it was damn hard to repay those banks. The time being post-Civil war, there was a lot of expansion industry wise, which lead to expansion population wise, which lead to expansion money wise (pennywise). This made the worth of the dollar grow constantly. On top of the bank charging interest, there was the natural interest (if you could call it that) of having to pay the bank even more than they borrowed, since the dollar was worth so much more.