High Quality Content by WIKIPEDIA articles! The McMillan Reservoir is a reservoir in Washington, D.C. that supplies the majority of the city`s municipal water. It was originally called the Howard University Reservoir or the Washington City Reservoir, and was completed in 1902 by the U.S. Army Corps of Engineers. The reservoir was built on the site of Smith Spring, one of the springs previously used for drinking water. Washington`s earliest residents relied on natural springs but this came to be inadequate as the city`s population grew. In 1850, Congress determined that the Potomac River should be the city`s principal source of water.