McNamara's Band wasn't written until 1889.
Wild Bill Hickok's death is featured before General Custer departs for the Little Bighorn. In actuality, Custer was killed June 25, 1876 and Hickok on August 2, 1876. Furthermore, Jack McCall was tried for the murder of Hickok and executed on March 1, 1877, and certainly not killed during an Indian attack the previous summer as depicted.