The United States invades Mexico under the banner of Manifest Destiny. The Treaty of Guadalupe Hidalgo ends the Mexican war the same year. Under this treaty, half of the land area of Mexico, including Texas, California, most of Arizona and New Mexico, and parts of Colorado, Utah, and Nevada is ceded to the United States. The treaty also gives Mexican nationals one year to choose United States or Mexican citizenship. Approximately 75,000 Mexican nationals decide to stay in the United States.