Steve Young, who played professional football for the San Francisco 49ers (among other teams), plays "Bro. Niner." During his scene in the film, Bro. Niner quotes Brigham Young; Steve Young is a direct descendant of Brigham Young.
While performing for students at the University of Missouri, Jonathan tells the crowd where his car is parked so that they can "steal all of (his) stuff" and burn it to the ground. This comment refers to the infamous "Extermination Order" against the LDS (Mormon) Church, issued by Missouri Governor Lilburn W. Boggs on October 27, 1838. This order called for the Mormons to be driven from the state or wiped out. (It was not formally repealed until 1975.)
The phone number listed on the wall at the auto mechanic's shop is 867-5309, from the Tommy Tutone song "Jenny (867-5309)." This number is also referenced in the other Halestorm films "The R.M." and "Church Ball."