Texas Rangers Anachronism
I think it's really weird that Fitzgerald tells this story about his father being down with the Texas rangers, and this movie takes place in 1823.
The rangers didn't really even form or have any significance before 1823. In fact the first mention of them is in 1823, and then they were officially formed in 1835 by the Texas government. That just seems like a really dumb mistake to me.
https://tshaonline.org/handbook/online/articles/met04