Though based on historical events, Arthur Miller altered some events to more strongly parallel his own experience during the McCarthy era. In particular, Abigail Williams was only 12. Miller made her older so that she could have had a sexual relationship with John Proctor. This paralleled Miller's own adulterous relationship with Marilyn Monroe.
Playwright Arthur Miller got his inspiration for "The Crucible" during the Hollywood black-listings. It reminded him of the paranoia, the finger-pointing and the all around outrageousness that the Salem Witch Hunt had possessed. Miller himself was called before The House of Representatives' Committee on Un-American Activities in 1956 to testify against his friends and, like his character John Proctor, refused to implicate them.
Kirsten Dunst auditioned for the role of Abigail Williams. She impressed everyone and was asked back to several callbacks and even did a screen test, but the producers and director ultimately decided that she was too young.
The open casting call for this movie was held at the abandoned Danvers State Hospital in Danvers Massachusetts, where the movie Session 9 was filmed, the auditions were held in the auditorium of the abandoned hospital which is prominently featured in Session 9.
During Melanie Lynskey's January 2015 interview with Marc Maron, she says that she auditioned for a role in The Crucible and went as far in the casting process as reading with Daniel Day-Lewis, but she didn't get the part. She didn't say which part she auditioned for, but she did specify that it was not the role of Abigail Williams (the part Winona Ryder eventually played).
The trivia item below may give away important plot points.
Before they are hanged, Proctor and the other accused witches recite the Lord's Prayer. This is to prove they are not witches, as it was believed that nobody in league with the Devil could recite the prayer.