Early in the film there is a scene where some Klan members are shooting up the house of a white woman because she is dating a black man. They wait for the second floor bedroom light to come on before they start shooting, but when the film cuts back to the scene outside a second later the bedroom light is not on.
One of the voting members, a heavy set white male was wearing long hair for this time period. Most southern white males did not wear their hair long, as such hippie type.
Sam Rockwell clearly has a pierced left ear, which was not the case with the real C.P. Ellis, but in general is something a Southern KKK leader would NEVER have done.
There is a scene at a baseball game at the start of the film where a player is shown wearing Nike branded baseball cleats, first made in 1980.
The gas station displayed prices for regular and unleaded gasoline. It is unlikely that an NC gas station would have had unleaded gas in 1971.
At the 2:04 mark, C.P. is talking to someone about an incident at the hardware store. C.P. is seen face on. As the shot changes to view C.P. from behind, he is obviously still saying something but there is no dialog until the shot changes back to view C.P. face on again.
On the plaque honoring Claiborne as Exalted Cyclops of the Year, misspellings include "Claibourne" and "exhalted".
During one of the first charrette meetings that Bill Riddick holds in a classroom, the word "committee" is misspelled several times on the blackboard behind him as "commitee."
Supposed expert shooting instructor closes his eyes as he fires a pistol at a target while talking to C.P. Ellis. Would never happen.