The war began in 1845 because;
The Mexican-American War was a conflict between the United States and Mexico, fought from April 1846 to February 1848.
Another reason was;
It stemmed from the annexation of the Republic of Texas by the U.S. in 1845
The final reason was;
and from a dispute over whether Texas ended at the Nueces River (the Mexican claim) or the Rio Grande (the U.S. claim).
Then in 1848, the peace treaty was signed. This treaty added an additional 525,000 square miles to United States territory, including the land that makes up all or parts of present-day Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming.
The treaty also said;
that Mexico ceded over 525,000 square miles of territory to the United States in exchange for $15 million and the assumption of Mexican debts to American citizens, which reopened the slavery issue.
The most important outcome was de facto independance because In 1845 the U.S. annexed the Republic of Texas, which had won de facto independence from Mexico in the Texas Revolution
