Mary Bonauto, a Maine attorney who led arguments before the U.S. Supreme Court in the case that legalized same-sex marriage, is being recognized by President Biden with one of the nation’s top civilian honors.

Bonauto is among the 20 Americans named Thursday as recipients of the Presidential Citizens Medal, an award given to citizens who have performed exemplary deeds of service for their country or fellow Americans.

Bonauto fought to legalize same-sex marriage in Vermont, Massachusetts, Connecticut and Maine before arguing before the Supreme Court in 2015 in Obergefell v. Hodges, which established marriage equality in all 50 states.

“Her efforts made millions of families whole and forged a more perfect Union,” the White House said in a written statement Thursday.

President Biden awards the Presidential Citizens Medal to Mary Bonauto during a ceremony in the East Room at the White House on Thursday. Mark Schiefelbein/Associated Press

Bonauto, 63, lives in Portland and works as senior director of civil rights and legal strategies for Boston-based GLBTQ Legal Advocates & Defenders.

“I’m totally astonished,” she said during a brief phone interview Thursday afternoon from Washington, D.C., where she was preparing for the awards ceremony at the White House.

Bonauto began her career in private practice in Portland in 1987 and started work with GLAD Law in 1990. In 1997, she was one of the attorneys who sued Vermont for not allowing civil marriages, leading to the creation of civil unions.

She also won the nation’s first case regarding same-sex marriage, allowing same-sex marriage in Massachusetts in 2003.

“People think about marriage as a personal thing, which it is, or a religious thing, which for some people it absolutely is,” Bonauto said during the interview Thursday. “It’s also a legal thing and for much of our country’s history and even before we had a constitution, it was considered an incredibly important personal right. It’s grounded in the idea that we should be equal and be able to pick our spouse, and that we pick our spouse, not the government.”

In 2012, Bonauto played a key role in the Maine citizen initiative and referendum vote that made Maine the first state to allow for same-sex marriage by popular election.

In 2015, she was selected as one of the lead attorneys to represent gay couples in Ohio, Michigan, Kentucky and Tennessee before the nation’s highest court and made arguments to allow them to marry and have their marriages recognized in their home states.

Bonauto said winning that case was “an incredible relief.”

“I knew nobody wants to feel insecurity about their family or that their family is a political football,” she said. “The idea that now it’s nationwide and not state-by-state, that this right is so basic that it now belongs to all Americans including LGBTQ Americans, I knew that was going to provide a lot of security and happiness to a lot of people.”

Rep. Chellie Pingree of Maine, D-1st District, said the award for Bonauto is well-deserved.

“I am thrilled to congratulate Mary Bonauto, a trailblazer from Maine, on being awarded the prestigious Presidential Citizens Medal,” Pingree said in a written statement. “Mary’s relentless dedication to justice and equality has transformed the lives of countless Americans.”

The Presidential Citizens Medal is among the highest honors that may be bestowed upon civilians in the United States. Other recipients this year include former U.S. Rep. Liz Cheney, R-Wyoming and former U.S. Sens. Chris Dodd, D-Connecticut, Ted Kaufman, D-Delaware and Bill Bradley, D-New Jersey.

Biden is also giving the award to Frank Butler, who set new standards for using tourniquets on war injuries; Diane Carlson Evans, an Army nurse during the Vietnam War who founded the Vietnam Women’s Memorial Foundation; and Eleanor Smeal, an activist who led women’s rights protests in the 1970s and fought for equal pay.

Other honorees include photographer Bobby Sager and Frances M. Visco, the president of the National Breast Cancer Coalition.

This report contains material from The Associated Press.