Pier 91 was used by the U.S. Navy from 1930 to the 1970s for the loading of ships including ships containing munitions. Over the years, military munitions were discarded into the Waters of Elliot Bay.

The Navy purchased the piers from the Port of Seattle in the early 1940’s and eventually, the Navy purchased the surrounding land and developed the area north of the piers as a supply depot and a receiving station. Piers 90 and 91 became the focus of the Seattle Port of Embarkation and tens of thousands of troops passed through there enroute to combat in the Pacific. Although scaled back after World War II, the Naval Supply Depot continued to serve the Navy and other military service branches through the Korean War and into the Vietnam War. However, it was eventually superseded by a new Naval Supply Center across Puget Sound at Bremerton. The Navy announced closure of its Smith Cove facility in March 1970.