The 1990 Census of Population and Housing the twenty-first decennial census of the United States was taken as of April 1, 1990, by the Bureau of the Census, an agency of the U.S. Department of Commerce. This census covered the 50 States, the District of Columbia, Puerto Rico, the Virgin Islands of the United States, and the Pacific island territories (American Samoa, the Commonwealth of the Northern Mariana Islands, Guam, and, by special agreement, the Republic of Palau).