This article summarizes an inventory of municipal water supply facilities in communities of 25,000 or more population conducted by the U.S. Public Health Service (USPHS). The summary includes detailed tables by state, population size group, and drainage basin, and is confined to national totals only. The inventory is compiled in cooperation with the appropriate state agencies, biennially for communities of 25,000 or more, and every 5 years for communities of 100 persons and above.