In 1966 Hirshhorn donated much of his collection, consisting of 6,000 paintings and sculptures from the 19th and 20h centuries (and constituting one of the world's largest private art treasures), to the United States government, along with a $2 million endowment. The Smithsonian Institution established the Joseph H. Hirshhorn Museum and Sculpture Garden in Washington, D.C., in 1966 to hold the collection; the museum opened in 1974. At Hirshhorn's death in 1981, he willed an additional 6,000 works and a $5 million endowment to the museum.