The American Bar Association has honored Mary Bonauto, a civil rights attorney in Portland, for her work advancing the rights of lesbian, gay, bisexual and transgender people.

The American Bar Association Commission on Sexual Orientation and Gender Identity presented Bonauto and two others with its new Stonewall Award at a reception Saturday at the association’s midyear meeting in Dallas.

Bonauto is the civil rights project director for Gay & Lesbian Advocates & Defenders Civil Rights in Boston. As a lawyer and advocate for GLAD since 1990, she has been at the forefront of the effort — locally, in New England and nationally — to legalize same-sex marriage.

“I was surprised. I didn’t know there was such an award,” Bonauto said in an interview Monday, describing her reaction to the news several months ago that she would receive the award. “It’s great to be acknowledged by your colleagues.”

It “says a lot” that the American Bar Association created the Stonewall Award to recognize lawyers who are active in the gay-rights movement, Bonauto said.

Bonauto co-led GLAD’s efforts in two challenges to the federal Defense of Marriage Act. She is now coordinating the amicus brief strategy in Windsor v. United States, a challenge that will be argued before the U.S. Supreme Court.

The Defense of Marriage Act, passed by Congress and signed into law by President Clinton in 1996, defines marriage as a legal union between one man and one woman.

Bonauto said she expects several dozen briefs to be filed in Windsor v. United States by March 1, in advance of oral arguments before the Supreme Court on March 27. She expects the case to be decided by the end of June.

Bonauto received the Stonewall Award along with Matt Nosanchuk, of the U.S. Department of Homeland Security in Washington, D.C., and Mia F. Yamamoto, a criminal defense lawyer and human rights activist in Los Angeles.