Factual error: The El Paso newspaper is dated Monday June 15 1872. June 15 1872 was a Saturday. (00:48:14)
Factual error: There's a plane in the sky above Clint's hat in the shooting hats scene.
Factual error: Two errors. The money in the safe is Confederate. It was worthless in 1872. Tucumcari didn't exist in 1872. The place which later became Tucumcari only came into existence in 1901 and wasn't named as such until 1908.