In 1942, the Department of Defense acquired land in St. Mary’s County and began construction of the Patuxent River Naval Air Station, which played a crucial role in testing airplanes used on World War II aircraft carriers. The base brought a surge in population and added technical jobs to the county’s traditional agricultural and maritime economy. After World War II, Patuxent River remained a testing center for aircraft and served as the training site for the first astronauts. Today it continues to play a vital role in testing cutting-edge aircraft for the U.S. Navy and is the largest employer in St. Mary’s County.