News Mary Jo Detweiler, Prince William’s first female library director, dies at 80 By Potomac Local News Published March 10, 2022 at 1:00PM Mary Jo Detweiler, the first female library director in Prince William County, led the system from 1975 to 1985. This article is FREE to read. Please Sign In or Create a FREE Account. Thank you. Author Potomac Local News View all posts #News