Fort Selden was a United States Army post, occupying the area in what is now Radium Springs, New Mexico. Established in 1865 for the purpose of protecting westward settlers from Native American raids, the post fell into disrepair after the American Civil War. It was ultimately abandoned in 1891, due in large part to the decision to expand Fort Bliss and the lack of any expenditures for repair of the facility.
The present day ruins are available for viewing via an interpretive trail. A visitor center offers exhibits on frontier and military life. Fort Selden State Monument is located 13 miles (21 km) north of Las Cruces, New Mexico, off Exit 19 of Interstate 25, near Radium Springs, New Mexico.