The 1990 United States Census was the 20th census conducted in the United States. It was conducted by the Census Bureau, which is part of the United States Department of Commerce. The census is conducted every ten years and is used to gather information about the population of the United States. This information is used to apportion congressional seats, as well as to provide data for the distribution of federal funds. The 1990 census marked the first time that the census was conducted primarily by mail. This allowed for a more efficient and cost-effective method of gathering information, as well as allowing for a more accurate count of the population.