The location where the angels get picked up to ride the bus to Hell is the same location used in two episodes of Breaking Bad; John B. Robert Dam, Albuquerque, New Mexico was where they shot the Extractor's pickup point.
The US flag in the opening shot has 38 stars and was in use from 1876 to 1889.
Jesse is leaving a message for Tulip and says "For me, it's just you, till the end of the world." The final episode is "End of the World".
A Wilhelm scream is heard during the massacre in the saloon.