This admission ticket admitted one to the South Dakota Calvary Band concert at the Coliseum on February 17, 1919.  I believe the venue is the Coliseum in Sioux Falls, South Dakota, that was built in 1917.

The writing on the back reads, To Mrs...  From Mrs. A. Harris, With Love.

Measures 3 13/16" x 2 1/8".  It's discolored from age and has some wear to the corners.