What led to disunity among Mexico

The result of the Mexican American War was the Treaty of Guadalupe Hidalgo in 1848, which stated that Mexico had to give up land to the United States, including Texas. That land now makes up the states of California, Utah and Nevada, as well as parts of Colorado, Wyoming, New Mexico and Arizona. The treaty also established the national border of Mexico at the Rio Grande River.

Explanation:

wait history, who want to talk about history, boring.

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: