During World War I, Woodrow and Edith Wilson kept a flock of sheep on the White House grounds to save costs to cut the grass. The wool was also auctioned off to raise money for the Red Cross. c. 1920-1924, by Martin A. Gruber. Black and white print, Smithsonian Institution Archives, RU007355 - Martin A. Gruber Photograph Collection, 1919-1924.
Photo and caption from The Bigger Picture: Visual Arts and the Smithsonian
Hat tip to Peter Kurilecz