What were the black codes?

limit African american freedom

Explanation:

After Andrew Johnson became the new president, White southerners Seeking a way to control the freedmen, created distinctive law enforcing codes, These codes were called the Black codes. Following the American Civil War, Southern states in the United States implemented the Black Codes, which limited African Americans' freedom and forced them to work in a labor economy based on low salaries or debt.

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: