Came across this happy snap at www.shorpy.com, and then found it on the Library of Congress site.
http://hdl.loc.gov/loc.pnp/npcc.16039
Library of Congress Prints and Photographs Division Washington, D.C. 20540 USA
UPDATE (more information from Shorpy site): ‘July 9, 1926. Washington, D.C. “Girls in bathing suits with ukuleles.” Identified in the caption of another photo as Elaine Griggs, Virginia Hunter, Mary Kaminsky, Dorothy Kelly and Hazel Brown.’
The Backward Ukulele Player 
[…] [4] The Library of Congress holds a photograph from 1926 of five happy young women with ukuleles, but I cannot say how they got them. Photograph at http://hdl.loc.gov/loc.pnp/npcc.16039 Library of Congress, Prints & Photographs Online Catalog, http://lcweb2.loc.gov/pp/pphome.html (accessed 5 April 2009). I first found this picture on http://www.shorpy.com, a site that holds a wealth of vintage photography. (See Happy Girls with Ukuleles — 1926) […]