Sketch from the Office of the Mexican Boundary Survey, n.d.

This area south of the Rio Gila, sketched by U.S. Boundary Commissioner William H. Emory, is now part of Arizona. The red line shows the U.S.-Mexico border before the United States purchased the adjacent land from Mexico in 1853. Secretary of War Jefferson Davis gave Army engineers this map to explore a southern railroad route to the Pacific.

Records of the U.S. House of Representatives, National Archives and Records Administration