Who is Michael Hanlon from It and what is their importance?

Michael Hanlon is the head librarian at the Derry Library. Mike is also an amateur historian, collecting stories about his hometown in order to preserve them for future generations. However, the things Mike uncovers in his research causes him to believe that something evil exists in Derry. Mike learns about mass murders, tragic explosions, and racially motivated fires that encircle periods of large amounts of child disappearances and deaths in Derry. All of these events cause Mike to recall the summer of 1958 when he was the member of a tight group of children who attempted to kill the monster they believed was responsible for the deaths of many of their classmates.