The description of this photograph offered by the US Library of Congress says,
"Sunday morning mass in camp of 69th N.Y.S.M.
Date Created/Published: [photographed 1861]
Father Thomas H. Mooney giving religious service, in front of tent, to New York State Militia, in Washington, D.C. area(?)."
Notice that there are both women and children in this small congregation.
Courtesy of the US Library of Congress.