Mary Jo Detweiler, Prince William’s first female library director, dies at 80

Mary Jo Detweiler, former Prince William County Public Library Director, passed away on February 25 at age 80.

According to her obituary, Detweiler was the first woman to hold the position. She managed the library system from 1975 to 1985, when the county had only two libraries — Central Library, at 8601 Mathis Avenue, and the Potomac Branch Library, 2201 Opitz Boulevard.

Detweiler continually pushed to expand the library system to offer more services to county residents. She was instrumental in establishing a “mini” library system known today as “neighborhood” libraries.

Don Wilson, a county public library employee since 1979, was tasked with the dual role of collecting information about the county’s local history while expanding the services the libraries offered to adults.

“I remember her as always, being friendly, easy to talk to,” said Wilson, who worked in the library administrative office with Detweiler, which, at the time, was inside Central Library. ”She kept an eye on what was going on, and a lot of the things that she dealt with were trying to convince the Library Board [of Trustees] and the Board of Supervisors to build more libraries.”

Initially, Detweiler pushed county leaders to build more extensive branch libraries before the county built its mini-library system. In 1982, county voters saw the start of a series of failed bond referendums that would have the more extensive libraries, said Wilson.

Eventually, the Chinn Park Branch Library in Lake Ridge and Bull Run Branch Library near Manassas opened in 1991 and 1994, respectivley.

After resigning from the library, Detweiler and her husband, Bill, moved to Alexandria. Detweiler built on her library experience by pioneering early library computer systems with Dynix, providing library staffing services for federal agencies, and teaching library science classes at Catholic University and George Mason University.

At the end of her career, she served as a librarian at the Virginia Theological Seminary, an Episcopal seminary in Alexandria.

According to her obituary, Detweiler died peacefully at home shortly after celebrating her 80th birthday with her children, their spouses, all four grandchildren, and a fabulous chocolate cake.

There are now 12 library locations in Prince William County. In Summer 2020, the Board of County Supervisors voted to dissolve the Board of Library Trustees and fold the independent library into the operations of the county government.