Announced in May 2001 by the US Geological Survey (USGS), this site provides access to water-resources data collected at approximately 1.5 million sites in all 50 states, the District of Columbia, and Puerto Rico. The data is accessed via several categories, including real-time, surface water, ground water, and water quality. Within each section, users have multiple options to narrow their searches. Descriptive information on each site in the USGS database is also available.