Continuity mistake: In the scene where Nikki brings the freezer to Juniper Creek, the freezer is strapped with a wide yellow strap to a hand truck. She leaves the freezer in the middle of the road. The freezer is now free of the hand truck and yellow strap. She gets in her pick up truck and the freezer is shown in the road strapped to the hand truck. She then proceeds to run the freezer over, but it is no longer on the hand truck. The hand truck and yellow strap are no where to be seen.
Other mistake: In episode 1x7, Barb has a list of all the family members' names and birthdays. On the list, the oldest daughter is a listed as "Amanda Henrickson". Her name is Sarah Henrickson: it's the actress who portrays her who is called Amanda (Seyfried).
Factual error: There is a cross on the wall in Bill and Barbara's bedroom. Mormons (of any persuasion) do not venerate or use the cross as a symbol of their faith.
Factual error: Season 5: Episode 8. The statue of limitations on statutory rape is 4 years. The police wouldn't even look into this case.
Factual error: In Utah you can legally marry at age 16. In Colorado, where the third wife is from, the legal age is 15. All that fuss that she lied when she married at 16 is moot.