Although Brian Donlevy was almost 49 when he made this film, the real William Quantrill was only 27 when he died. Marguerite Chapman was 32 when the film was made and plays Quantrill's woman, Kate Clarke, a fictional character. In real life, Quantrill met a local Missouri girl, Sarah Katherine King, when she was only 13. She lived in camp with Quantrill and his soldiers. They married and she was 17 when he died.

Kansas became a state January 29,1861, about 2 1/2 months before the start of the U.S. Civil War (April 12,1861- April 9, 1865).

The Lawrence massacre, August 21 1863 (also known as Quantrill's raid) was an attack during the American Civil War by the Quantrill's Raiders, a Confederate guerrilla group of about 450 men led by William Quantrill, on the Unionist town of Lawrence, Kansas. 150-190 unarmed civilians were murdered during the massacre. The banks and stores were looted and the town was burned during the four hour raid.

An early scene in the movie shows the gang talking about Lawrence, Kansas and that it would be big enough for a Union Army detachment. This movie is set after the start of the US Civil War (1861-1865). Lawrence, Kansas had a population of 1,645 in 1860 and 8,320 ten years later. The estimated population of Lawrence in 2018 was 97,286.

Historical inaccuracy: The movie shows Jesse James (Audie Murphy) killing "Bloody Bill" Anderson (Scott Brady) during an argument over treatment of a prisoner during the "Lawrence Massacre". In real life, the Union Army tracked down Anderson and he was killed during a gunbattle in Albany, Missouri on October 26,1864 more than a year after the Lawrence, Kansas action.