Doña Ana County is located in the southern part of the State of New Mexico, United States. As of the 2020 U.S. Census, its population was 219,561, which makes it the second-most populated county in New Mexico. Its county seat is Las Cruces, the second-most populous municipality in New Mexico after Albuquerque, with 111,385 as of the 2020 U.S. Census.

The San Andres Mountains are a mountain range in the southwestern U.S. state of New Mexico, in the counties of Socorro, Sierra, and Doña Ana. The range extends about 75 miles (121 km) north to south, but are only about 12 miles (19 km) wide at their widest. The highest peak in the San Andres Mountains is Salinas Peak, at 8,965 feet (2,733 m).