John Disturnell, Mapa de los Estados Unidos de Méjico (1847)

The Mexican-American War was fought from 1846 to 1848 over the United States' 1845 annexation of Texas, which had gained its independence from Mexico in 1836. The annexation of Texas had previously been a controversial topic in the United States because it would have upset the balance between slave and free states. However, U.S. President James Polk, who believed in the United States' "manifest destiny" to expand, wanted to add the territory.  It turned to conflict after the Mexican government, unhappy with the proposition that the U.S. southern border should stretch all the way to the Rio Grande, refused to negotiate the United States' proposed purchase of the the territory. After capturing Mexico City, the United States emerged victorious, and on February 2, 1848, the two countries signed the Treaty of Guadalupe Hidalgo to end the war. This map, created by John Disturnell in 1847, was used for reference during the treaty negotiations. The agreement stated that in exchange for 15 million dollars, the United States would own Texas, as well as 525,000 square miles of land spanning across California, New Mexico, Utah, Nevada, Arizona, Colorado and Wyoming. The treaty also established the new 2,000 mile border between the United States and Mexico at the Rio Grande and Gila River. The map depicts all of the land within the Mexico Territory before the war, highlighting the sheer amount of land the United States acquired from Mexico. However, it also contains significant errors. Most notably, El Paso was placed 42 miles north of its true location, which eventually led to further border disputes between the United States and Mexico and resulted in the Gadsden Purchase.