With the addition of Ritts's photos, the MFA collection now comprises more than 5,000 works from as far back as the 1840s. The collection started in 1924, when Alfred Stieglitz donated 27 of his photographs to the museum. In 1950, Georgia O'Keefe, Stieglitz's widow, donated many more. The collection now includes the works of Ansel Adams, Charles Sheeler, Edward Weston, Imogen Cunningham, Josef Sudek and Yousuf Karsh. The museum has nearly 200 of Karsh's photos, including black-and-white portraits of Winston Churchill, Audrey Hepburn and Ernest Hemingway.