During WWII, women went to work in factories while the men were away from war, this actually helped the unemployment rate drop since women were actually being used for something other then just being a "house wife", which was common in that time. Since we were just coming out of the great depression, it was hard for America to have the money to actually make weapons and have a war that we could actually fight.
Your answer is that the main reason is that people buy land and they needed to get money which means there really greedy people so the buy slaves and force them to work for little or no money so they can sell crops (they made the slaves become farmers) to make profit then they would buy more land and get more slaves to work as farmers on and on. So it spread because one guy did it and he made a lot money and other people wanted to do the same and that's how slavery spread through North America.
Answer:
In this fashion the odometer, called the roadometer, was invented in 1847 by the Mormon pioneers crossing the plains from Missiouri.
Explanation: The odometer was attached to a wagon wheel as the wagon trav- eled. It was developed by William Clayton and Orson Pratt, and built by carpenter Appleton Milo Harmo
