IT timeline

1715: It painfully awakes.

1740-1743: It starts a three-year reign of terror that culminates in the disappearance of over three hundred settlers from Derry Township (similar to the lost Roanoke Colony, which was founded as a logging town.)

1770: It once again awakes.

1851: IT awakes when a man named John Markson poisons his own family, then commits suicide by eating a white nightshade mushroom, causing an excruciating death.

1876 – 1879: It awakes, then returns to hibernation after murdering a group of lumberjacks who were later found near the Kenduskeag Stream.

1904: It awakes when a lumberjack named Claude Heroux murders a dozen men in a bar with just one axe. Heroux was promptly pursued by a mob of townsfolk and hanged. In 1985, when Mike asks a witness, if he saw anyone he didn't know that night or seemed out of place. He remembered seeing "a comical sort of fella". He also said he had seen him a few more times since.

1906: It returns to hibernation when the Kitchener Ironworks explode, killing 108 people, 88 of whom were children at an Easter egg hunt.

1908: It awakens after the KItchener Ironworks explosion, where 102 people die (88 kids and 14 adults).

1929: It awakes when a group of Derry citizens ambushes and kills the Bradley Gang, a group of robbers and murderers. The town, including its police chief, pretends it never happened. However, a witness later recounts the tale to Mike Hanlon, including seeing a clown in farmer's attire participating in the slaying.

1930: It returns to hibernation when the Maine Legion of White Decency, a Northern counterpart to the Ku Klux Klan, burns down "The Black Spot", a nightclub known to cater to African-Americans at the nearby army base. IT appears at the location as a giant bird with balloons on its wings, witnessed by Mike's father William Hanlon.

1935: It awakens after the Bradley Gang shootout.

1946: William "Bill" Denbrough is born.

1951: Georgie Denbrough is born.

1957: It awakes when Dorsey Corcoran is beaten to death by his stepfather, Richard Macklin. In October, Georgie Denbrough dies from blood loss, when his arm is torn off by Pennywise. This prompts Bill Denbrough (Georgie's older brother) to investigate, leading to the discovery of IT. He, along with several other victims of IT's torment, performs the Ritual of Chüd, which wounds It and forces it to return to an early hibernation.

1962: It awakens when The Black Spot is burned down by a cult.

1984: It awakens when three bullies assault Adrian Mellon and Don Hagarty, a homosexual couple. The bullies throw Mellon off a bridge and IT, in the form of Pennywise, attacks and kills him.

1985: It is finally defeated and physically killed in another Ritual of Chüd by the adult Bill, Richie, Beverly, Eddie, and Ben.