Evan Wolfson, a Squirrel Hill native, was named by Time magazine in 2004 as one of the 100 most influential people in the world for his work as founder and president of the advocacy group Freedom to Marry.
But in his home state, same-sex marriage is still a long way off.
Mr. Wolfson, 54, said the recent legalization of gay marriage in New York sets an example for its neighboring states and the rest of the country.
It also casts light on the state of gay rights in Pennsylvania, where neither same-sex marriage nor civil unions are allowed -- and where state Rep. Daryl Metcalfe, R-Cranberry, introduced a constitutional amendment in May to define marriage in Pennsylvania as being only between a man and a woman.
"It's very painful for families in Pennsylvania who see, just across the border, real progress being made and feel that Pennsylvania needs to treat everyone more fairly," said Mr. Wolfson, a civil rights attorney in New York.
Mr. Metcalfe said the move in New York could form a galvanizing point for opponents of same-sex marriage in Pennsylvania. "It's certainly going to create more momentum here in Pennsylvania," he said last week. "It's an issue that I'll be working on, and I'm sure that I'll have more support now."
Malcolm Lazin, executive director of Equality Forum, a nonprofit that seeks to advance lesbian, gay, bisexual and transgender, or LGBT, civil rights, told the Philadelphia Inquirer last week that Pennsylvania was "a backwater when it comes to gay equality."
State Rep. Dan Frankel, D-Squirrel Hill, said that with a Republican state House, Republican state Senate and a Republican governor, the current political climate is particularly unfriendly toward same-sex marriage.
Even when Democrats controlled aspects of state politics in the recent past, Mr. Frankel was unable to pass House Bill 300, which he said was less politically charged than the marriage question. That bill would amend the Pennsylvania Human Relations Act to outlaw discrimination on the basis of "sexual orientation" and "gender identity and expression" in employment, public accommodations and housing.
"Right now, in Pennsylvania, you can fire [people] because they're gay, you can refuse to rent an apartment, you can deny them access to higher education," he said. "That's, in my view, an outrage and an embarrassment that Pennsylvania still has a form of legalized discrimination. We have to get over that hurdle before we address the issue of marriage equality."
Mr. Wolfson, who regularly visits his family in Pittsburgh, agreed. "Pennsylvania really needs to start moving in the direction of helping the families who live across the state who are being harmed by the exclusion from marriage," he said.
In March, he spoke at the University of Pittsburgh School of Law at the invitation of the American Civil Liberties Union. While in town, he also spoke at Allderdice High School, where he graduated in 1974.
"It was extremely moving how strong and hopeful students are today, and how deeply gay and non-gay students believe in treating all people fairly," he recalled.
Heartened by that visit, he hopes the example set by New York will aid gay rights advocacy efforts in Pennsylvania.
"People in Pennsylvania will get to see, right across the border in New York, that none of the bad things the opponents try to scare people about are true, and that everyone is better off when everyone is secure in their families," he said.
He said the passage of the New York bill, the first one that a Republican-led chamber of a Legislature -- the state Senate -- voted to advance, shows the issue can be bipartisan. Six national polls since last August show a majority of Americans support marriage rights for same-sex couples.
"This is not a Democrat versus Republican question, or a liberal versus conservative," he said. "This is a question of fairness, family and freedom."
Freedom to Marry, which was founded in 2003, will continue to focus its efforts on discriminatory federal law and the 44 states that do not allow same-sex marriage, Mr. Wolfson said.
Mr. Frankel also hopes the move in New York will spur equality efforts elsewhere.
"I'm confident that it's inevitable; it is going to happen, just a matter of time," he said of gay marriage here.
"I just hope that Pennsylvania isn't the last state to the table."