Is American Horror Story season 7 based on true events?

Sorry to make all your nightmares a reality but American Horror Story is in fact based on several real events and historical figures. Much of the show's plot-lines are not make-believe, as you assumed.

Do you have to watch American Horror story in order?

Because "AHS" is an anthology series that reinvents itself with a new story and set of characters every season, fans don't necessarily have to watch all of the seasons, or all of them in order, to fully appreciate the ones they do get to see.

Who killed Mason Harris?

TheStrongGeek theorizes that Lee confessed to murdering Mason on tape at the Polk's House of Horrors to protect her child, since Flora only murdered Mason while possessed; she had no idea the evil she was inflicting on her own father.