A rare photo of Selina Gray, a slave of Robert E. Lee has been acquired by the National Park Service. The photo was bought on eBay for $700.

"It's extremely rare to have an identified photo of an enslaved person," said National Park Service spokeswoman Jenny Anzelmo-Sarles told the AP. "Since slaves were considered property, it's very rare to have a photo where you can identify the people in the photo."

Selina Gray was owned by the Lee family and served as the personal maid of Lee's wife, Mary Anna. When the Lee family abandoned Arlington House in 1861, Mary Anna Lee gave Selina Gray keys to the house, leaving her in charge.

Along with more usual valuables, the house contained heirlooms connected to George and Martha Washington, to whom Mary Anna was related. From the National Park Service:

The United States Army assumed control of the Arlington Estate on May 24, 1861. Later, U.S. Army officers occupied the house. When Mrs. Gray discovered some of the treasures had been stolen, she confronted the soldiers and ordered them "not to touch any of Mrs. Lee's things." Gray alerted General Irvin McDowell, commander of the United States troops, to the importance of the Washington heirlooms. The remaining pieces were sent to the Patent Office for safekeeping. Through Selina Gray's efforts, many of the Washington pieces were saved for posterity.

The photograph of Gray will go on display at Arlington House this Saturday at 2 p.m. as part of a new exhibit.