White Sands Missile Range (WSMR) is a United States Army rocket range of almost 3,200 sq mi (8,300 km) in parts of five counties in southern New Mexico. The largest military installation in the United States, WSMR and the 600,000-acre (2,400 km) McGregor Range Complex at Fort Bliss to the south (southeast Tularosa Basin and on Otero Mesa) are contiguous areas for military testing. It includes the site used for the first atomic bomb test, codenamed Trinity.