The Rio Grande, located within the states of Colorado, New Mexico, and the border of Texas and Mexico, serves as part of the border between the United States of America and Mexico. Prior to the Mexican-American War, Texas claimed the Rio Grande as its border with Mexico. Mexico did not acknowledge the claim and stationed soldiers north of the river. Texas used the positioning of these troops as reason for the United States to become involved. Following the Gadsden Purchase in 1853, the Rio Grande became the official border between Texas and Mexico.