Ginnie Cooper, who has overseen a $153 million remaking of the District’s public library system, said Wednesday she will retire before the year ends.

Under Cooper, chief librarian since 2006, the D.C. Public Library has renovated or rebuilt 14 branches — several of them designed by globally prominent architects — with two others set for overhauls. Library patronage and circulation has increased in that time, making good on a push by former mayor Anthony A. Williams and his successors to reinvigorate the public library system.

The recently enacted city budget includes two major library initiatives that can be considered capstones to Cooper’s tenure: a major expansion of library hours to nights and weekends, and the commitment of $103 million to rebuild the central Martin Luther King Jr. Memorial Library.

A D.C. Public Library release announcing Cooper’s departure included plaudits from Mayor Vincent C. Gray, who called her “one of the finest public servants I’ve worked with,” and longtime DCPL board chairman John W. Hill Jr., who called Cooper and her team “a key reason” for the library system’s improvement in recent years.

A Minnesota native, Cooper, 67, previously served as director of the public libraries in Alameda County, Calif., Multnomah County, Ore., and Brooklyn, N.Y. She encountered some controversy in Brooklyn, which followed her when she was named to the D.C. post, but she won early and sustained support after quickly moving to improve management of the neglected library system and improving conditions at the MLK Library, including her decision to remove metal detectors from the facility’s entrance. In the release, she said her departure from the District is “bittersweet.”

“While I look forward to what the future will bring, I will miss being a part of a team that works hard every day to provide great library service to residents of the District,” she said.

In a March interview, Cooper said she was most proud of her work revitalizing the city’s community libraries. “We have said, let them be beacons in their community,” she said. “Let them be places where people of all ages can come and be comfortable and learn and enjoy what it is that’s happening, and we’ve seen them used in exactly that way. . . . Those beautiful libraries draw people in.”

Hill said the board will undertake a national search for the library system’s next director. Cooper said she will remain as chief librarian, overseeing the expansion of hours and MLK renovation planning, until her successor is named.