Mesilla Valley

The treaty provided for a joint commission, made up of a surveyor and commissioner from each country, to determine the final boundary between the United States and Mexico. The treaty specified that the boundary, after following the Rio Grande River from the sea, would turn west from the river 8 mi north of El Paso. The treaty was based on an 1847 copy (the Disturnell Map) of a twenty-five-year-old map which was incorporated into the treaty. However, surveys revealed that El Paso was 36 mi further south and 100 mi further