The black & white glass plate photos shown during the credits were taken on set and developed on site by the photographer.
The land used in Minnesota for filming is privately owned by one of the extras. It is a paintball/airsoft field when not being used for movies or law enforcement training. The buildings used in the fight forest were originally built for airsoft and reenacting use.
The helmets worn by the black soldiers are the M1917 Helmet modeled after the British mark 1 Tommy helmets used during the war. However, more commonly black units during the war used the French Adrian helmet. This was due to American leadership passing command of colored units to the French army.
At the South Dakota premiere showing of this film on November 10, 2019, it was noted that the majority of the film's events happened exactly 100 years previously ... namely, November 10, 1919. The full range of the movie is from November 8/9 to November 11, 1919, but the significance of the screening date was appreciated by the audience in attendance at the Historic Orpheum Theatre in Sioux Falls, South Dakota.
While much of the movie was filmed in Minnesota, the scenes with General Pershing (Ron Perlman) and Colonel Jack Morrison (Billy Zane) were shot in Pasadena, California.