OMAHA, Neb. (AP) — Active members of the U.S. armed forces and their families are being offered free admission to Douglas County Historical Society’s General Crook House Museum in Omaha this summer.

The promotion runs through Sept. 1.

Both the General Crook House and the campus are of special significance to the American military. Fort Omaha was built as an Indian Wars United States Army supply installation, and later served the Signal Corps and as a training ground for the Army’s Balloon School. The school taught soldiers how to do reconnaissance from hydrogen balloons in preparation for World War I.