Because of the invention of the__cotton became the foundation of the southern economy.

The cotton gin

Explanation:

When Eli Whitney invented the cotton gin it provided a quicker method when it came to picking the seeds out of cotton. The faster the seeds could be picked out the more the plantation owners wanted a faster way to pick cotton.

answer: the time zones used to be whatever the local authority wanted them to be. one town might have 6am whenever the sun came up and another town had 6am 10 minutes later.  

the trains had a hard time when their orders said to be at a certain point at 6am.  

6am, but who's 6am.  

the railroads got together and set the time zones more or less along the longitude lines across the country.

explanation: