White Sands Missile Range (WSMR) is a United States Army military testing area of almost 3,200 sq mi (8,300 km2) 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 km2) McGregor Range Complex at Fort Bliss to the south (southeast Tularosa Basin and on Otero Mesa) are contiguous areas for military testing.On 9 July 1945, the White Sands Proving Ground was established for testing German and American long range rockets. Just seven days later, the first atomic bomb test, code named Trinity was exploded at Trinity Site, near the north boundary of the range.