Alamogordo is a city in and the county seat of Otero County, New Mexico, United States. A city in the Tularosa Basin of the Chihuahuan Desert, it is bordered on the east by the Sacramento Mountains and to the west by Holloman Air Force Base. The population was 31,384 as of the 2020 census. Alamogordo is widely known for its connection with the 1945 Trinity test, which was the first-ever explosion of an atomic bomb.