Siobhan Reardon, the longtime leader of the Free Library of Philadelphia, resigned Thursday, after employee complaints about racial discrimination in the workplace led Mayor Jim Kenney and some library trustees to pressure her to step down.

“It has been an incredible 12 years full of highs and lows, and we have achieved much during this time,” Reardon wrote in her resignation letter to the chairs of the two boards that run the independent library system. “I leave knowing that the mandate that the boards gave me years ago — to turn the Free Library into a world-class, 21st century library — has largely been achieved.”

The resignation is the latest local reverberation of the protests over the police killing of George Floyd in Minneapolis.

Workers have raised concerns about racial discrimination in the library system for years. But their efforts gained heightened visibility in late June after they formed a group called the Concerned Black Workers of the Free Library of Philadelphia and sent an open letter to management, saying they face discrimination on a regular basis, are paid less than white colleagues, and were being asked to return to work without a plan to keep them safe from the coronavirus.

The letter led at least six authors to cancel virtual Free Library events in solidarity with the workers, a key moment in their campaign to force changes.

Reardon’s resignation letter did not address recent controversies at the library. And there were early indications late Thursday of a backlash building against her ouster. While many Black employees who were critical of her leadership cheered the decision, some wealthy benefactors were planning to resign from the board of the Free Library of Philadelphia Foundation, a philanthropic group that supports the library.

At least four members of the foundation’s board, which is separate from the board of trustees that oversees the library’s operations, said Thursday that they would resign, according to one foundation board member. ”Many trustees and foundation board members are upset that Siobhan has been placed in this position because they feel that she has always acted in the best interest of the Free Library, that she’s been a wonderful leader, and that the situation that has been thrust upon her is unfair,” said the board member, who spoke on the condition of anonymity.

The resigning board members include Stephanie Naidoff, Sheldon Bonovitz, and Susan Smith

Pamela Dembe, who chairs the Free Library board of trustees, praised Reardon in an email to trustees.

"For a dozen years Siobhan Reardon has worked tirelessly and with great imagination, with the able inspiration and energy of our amazing library workers, to transform libraries,” Dembe wrote. “In the last several months, events have overtaken us all. The health consequences of COVID-19 and the long-overdue wider rage about deeply imbedded racism have brought us to a point where the Free Library, like many other institutions, must make very major changes if we are to most effectively serve our employees and our patrons.”

The Free Library has not announced a plan for replacing Reardon.

Reardon modernized the Free Library’s systems through ambitious information technology projects, expanded library hours from five to six days per week, and helped to launch a program in which incarcerated parents could read to their children over video. In 2015, the trade publication Library Journal named her librarian of the year.

Kenney, who had worked behind the scenes in recent days to force Reardon’s resignation, on Thursday thanked her for her service, but said the library needed to transition.

“The Free Library of Philadelphia strives to be a welcoming and inclusive public space, and that mission must endure,” Kenney said in a statement. “After hearing calls for reform from library employees and the public, it is clear that a change in leadership is necessary during these unprecedented times. Our administration stands in solidarity with the Free Library’s Black employees, and the countless others who have made their voices heard.”

The workers who had raised concerns about Reardon’s leadership applauded the resignation.

The Concerned Black Workers released a statement asking to be involved in the search for a new director and calling on Dembe, who had been a vocal supporter of Reardon, to step down as chair.

“Although Siobhan Reardon could have used the letter from the Concerned Black Workers as an inroads to being part of a culture of change and building trust, her refusal to change meant that resignation was the only way forward,” the workers said in the statement.

Andrea Lemoins, 43, a library community organizer in the Southwest cluster who helped write the open letter in June, said Thursday that Reardon’s departure “is the first step in really taking down white supremacy at the Free Library.”

She said issues with racial discrimination are most pronounced at the Parkway headquarters.

“What it looks like is getting paid less for doing the same job, getting abusive emails from Siobhan, being told as a Black person that you are overreacting, that you don’t understand what’s going on,” Lemoins said.

The new leader, Lemoins said, “should be a Black person. I want that person to have a history of fighting for the Black community ... and I want that person to have a track record of fighting against racism and bias.”

Michele Teague, a local area network administrator at the Parkway Central Branch, said she was ”thrilled, absolutely thrilled” about the resignation because Reardon “had an unwillingness to accept and hear what people were saying and feeling” regarding workplace racism.

”I said this to her on more than one occasion: You cannot heal what you refuse to acknowledge,” said Teague, who’s been with the library for 12 years. “She would not acknowledge that there was bigotry and racism. She never put any appropriate actions in place.“

Shahadah Abdul-Rashid, 33, a community initiative specialist in the Central Cluster who has been with the library for more than two years, said the departure of Reardon is “a first step in building an organization that is more equitable to all.”

Abdul-Rashid said Reardon “allowed things to be brushed up under the rug.”

”She kind of ignored it or pacified the situation,” Abdul-Rashid said. “She tried to satisfy everyone involved and didn’t take into account the people who were harmed.”

For example, Abdul-Rashid said, after she was bullied and racially harassed in 2018 at the Fishtown branch by white employees, she was moved to another branch.

“That did not address the behavior of the bullying employees,” Abdul-Rashid said. “I was just told that’s how people in Fishtown are.”