Factual error: We learn that the previous sheriff, Charlie Wade, took revenge on anyone who smuggled illegal immigrants across the border in the late 1950s - we are shown the smuggling, as Eladio Cruz hides a group of Mexican men in a watermelon truck to take them across the border. However, in the 1950s, the border was not fortified the way it is now - the smuggling shown would simply not have been necessary.
Continuity mistake: In the scene where Sam and Pilar start their walk to the river (after the ceremony at the courthouse), she states that she is on her lunch hour, but the sun and shadows show it is late in the day.
Factual error: In the scene where the colonel is counseling the private for her failed drug test, the rank insignia on her hat is turned up-side down. This mistake, along with the colonel's rank also being up-side down, leads me to wonder if it was done deliberately.