Since Montgomery County began issuing the licenses, Fetterman has officiated at 11 weddings for gays and lesbians bearing licenses from the other corner of the state. He says word spread after he told the host of a local radio program that he had no problem marrying same-sex couples.
In doing so, Fetterman, who sports tattoos and a goatee - along with a master's degree in public policy from Harvard - has only burnished his reputation as a maverick Democrat intent on revitalizing the working-class borough. He also stepped up where those other mayors - both better known as supporters of marriage equality - would not.
When New Hope Mayor Laurence D. Keller and Philadelphia's Mayor Nutter declined to officiate at same-sex marriages, both cited the unsettled question of whether the Montgomery County licenses were legal.
Fetterman said he was not afraid to do what he thinks is right - even if the state thinks he is wrong.
"Somebody could say it's not your call to make," he said. But when it comes to matters of civil disobedience, "Well, it's my choice."
To him, the state law defining legal marriage as between a man and a woman is unconstitutional.
The first couple he wed were John Kandray, 40, and Bill Gray, 41, of Swissvale, Allegheny County, who had dated steadily for 11 years.
They knew that the window of opportunity presented by Montgomery County Register of Wills D. Bruce Hanes' decision to issue the licenses could quickly slam shut - as it has.
So they called Fetterman, who quickly agreed and offered to host the ceremony in the old Chevrolet dealership he is renovating into a home for him, his pregnant wife, and two children.
He does not provide decorations or a buffet for the ceremony, and his idea of dressing up is the casual shirt and cargo shorts he might be wearing that day. Those frills didn't matter to Kandray and Gray.
"We had a marriage officiated by the mayor of Braddock the same way any straight couple could do," Kandray said.
Fetterman looks like the mayor who rode in on a Harley. But some of the tattoos on his arm - dates of people who were murdered in Braddock and the borough's zip code of 15104 - are evidence of his loyalty to the borough he has led since 2006.
He brags about its rich history, including the 1875 opening of Andrew Carnegie's first steel plant.
At its peak in the 1950s, Braddock's population was about 20,000. A poster child for the rise of suburbanization and the decline of the steel industry, it now has 2,300 residents.
Though the city still looks scruffy, it has become an alluring symbol of rebellious resilience under Fetterman, who was elected by one vote in 2005, and reelected in a landslide four years later.
New businesses and apartments have opened, he said. Braddock has been the setting for a Levi's commercial, a movie about the sport of extreme pogo, and a film starring Christian Bale and Woody Harrelson, Out of the Furnace, which is set to open this year.
He says his new policing strategies have reduced crime, and he has launched social-service and redevelopment projects.
Now, he said, "there's always a shortage of available housing in the area. I think we've elbowed our way into the decision matrix of young people's ideas of a neighborhood or community to live in."
He said his enthusiasm for using his mayor's office as a pulpit for gay marriage was not a sneaky way to build Braddock by attracting same-sex residents, who have been credited with rejuvenating some neighborhoods.
"Would I welcome a gay couple? I'd welcome any couple that moves to town. My involvement with same-sex marriage is strictly one of disappointment at others' unwillingness to perform the marriages," he said.
His actions, he said, are based on fairness.
"How is it that a gay couple that I'm marrying tonight can't be legally recognized in this state," he asked, "but if I were single, I could get on a plane tonight, meet a girl in Vegas, and get married by Elvis in a drive-through - and that's completely legal and legitimate?"
The same-sex couples he has met are "ordinary and American" as anyone, Fetterman said. "To anyone who thinks they're what's wrong with America, get a clue."
Contact Carolyn Davis at 610-313-8109, firstname.lastname@example.org, or @carolyntweets on Twitter.