Post Reply - WAR

The Mexican Cession, shown in red, and the later Gadsden Purchase, shown in yellow

Before the secession of Texas, Mexico comprised almost 1,700,000 sq mi (4,400,000 km²), but by 1849 it covered just under 800,000 square miles (2,100,000 km²). Another 30,000 square miles (78,000 km²) were sold to the U.S. in the Gadsden Purchase of 1853, a total reduction in Mexican territory of more than 55%, or 900,000 square miles (2,300,000 km²).^[236] Although the annexed territory was about the size of Western Europe, it was sparsely populated. The land contained about 14,000 non-indigenous people in Alta California^[237] and about 60,000 in Nuevo México,^[238] as well as large Native nations, such as the Papago, Pima, Puebloan, Navajo, Apache and many others. Although some native people relocated farther south in Mexico, the great majority remained in the U.S. territory.

The U.S. settlers surging into the newly conquered Southwest replaced Mexican law (a civil law system based on the law of Spain), which, in the Law of April 6, 1830, forbade any further immigration. However, they recognized the value of a few aspects of Mexican law and carried them over into their new legal systems. For example, most of the Southwestern states adopted community property marital property systems, as well as water law.

Many Mexicans, including mestizos, Afro-Mexicans, and indigenous peoples in the annexed territories, experienced a loss of civil and political rights. The Treaty of Guadalupe Hidalgo promised U.S. citizenship to all former Mexican citizens living in the territories. However, the United States gave ceded states the authority to establish citizenship policy, and within a year, states were passing laws that banned all Mexicans in Arizona, California, New Mexico and Texas from U.S. citizenship, except white male Mexicans.