Los Alamos County (Spanish: The Aspens) is a county in the U.S. state of New Mexico. As of the 2010 census, the population was 17,950. The smallest county in area of this state was administered exclusively by the U.S. federal government during the Manhattan Project, but now has equal status to New Mexico's other counties. The county seat is Los Alamos. The other population center in the county is White Rock.