Answer:
The boarder between the USA and Mexico what moved South.
Step-by-step explanation:
Mexico lost the Mexican-American War from 1846 to 1848. In doing so it lost about one-third of its land to the USA. Texas was taken and the boarder was changed to the Rio Grande. Mexico also ceded modern-day California, Nevada, Arizona, Utah and New Mexico. Some regions of Colorado and Wyoming were also included in this.