Strossen, 57, was the organization's longest-serving president and the first woman to hold the job. She is only halfway through her latest three-year term, but Strossen said she thought the national advocacy group could benefit from fresh leadership.

“There's new energy, new connections to different communities,” she said in a phone interview Friday.

Her last day will be Oct. 19. Strossen said she would remain involved with the ACLU, most likely as a fundraiser. The ACLU's governing board is to elect a successor in the fall.

Strossen became the ACLU's president in 1991, when the group's national reputation was mixed. Just three years earlier, Republican presidential candidate George H.W. Bush scored easy political points against Democrat Michael Dukakis by writing him off as a “card-carrying member of the ACLU.”

During Strossen's tenure, the group's formal membership and national staff grew substantially. The organization worked to expand in the country's midsection, where its presence and support had traditionally been weak.

“We've made quantum strides toward being a truly integrated organization that operates across the country,” Strossen said.

The group has been especially active since the Sept. 11 terrorist attacks, challenging U.S. government practices regarding espionage, prisoner interrogations and the detention of terrorism suspects.

While serving as the ACLU's president, an unpaid job, Strossen also taught full-time at New York Law School.

Strossen's tenure wasn't always met with accolades. She was loudly criticized in recent years by a faction of ACLU board members who argued that she suppressed dissent within the organization.

But she said the tumult and self-inspection had been healthy for the organization and that she remained convinced the group's work was more important than ever.