Washington (CNN) -- Barney Frank wasn't the first member of Congress to publicly reveal he was gay, but he was the first to do so voluntarily, he told reporters Tuesday in talking about his decision to retire.
Still, Frank said, he didn't come out about his sexuality until he was 47.
"So I was not the daring young man on the flying trapeze, but it worked out better than I thought," he said.
A prominent 16-term liberal Democrat from Massachusetts and archenemy of political conservatives nationwide, Frank announced Monday that he does not intend to seek re-election in 2012.
Now 71, Frank said Tuesday his decision was prompted in part by changes made to the boundaries of his U.S. House district.
As part of Massachusetts' recently concluded redistricting process, Frank's 4th Congressional District will lose the heavily Democratic blue-collar port city of New Bedford while gaining several smaller, more conservative towns to bring in more than 300,000 new constituents.
"I decided many years ago I will not be here when I'm 75," Frank said, saying that meant the 2012 election would have been his last.
"Everybody has a last term, and if you're talking about people that you've substantially represented, then that's not an obstacle," he said. "But then I would then be required to go to 325,000 people, some of whom I've never represented, and areas I've never been involved in, and say to them, look, here's the deal -- why don't you elect me and for the next two years I will be there to receive your problems and, by the way, by the end of 2014, I'm going to dump them."
President Barack Obama issued a statement praising Frank's public service, calling the congressman a "fierce advocate for the people of Massachusetts and Americans everywhere who needed a voice."
While Massachusetts' entire House delegation is Democratic, local Republicans insist Frank's retirement will put the reconfigured district in play.
"It is clear that Congressman Frank was not looking forward to another hard-fought campaign after losing his gerrymandered district and spending nearly every penny he had in 2010," Massachusetts Republican Party Executive Director Nate Little said in a written statement.
"Republicans were already gearing up for a strong race and Frank's sudden retirement injects added optimism and excitement into the election."
Frank, first elected to the U.S. House of Representatives in 1980, is the top Democrat on the powerful House Financial Services Committee. The controversial 2010 Dodd-Frank measure, designed to rein in Wall Street excesses after the 2008 financial collapse, passed the House without any GOP support.
Frank made headlines earlier in his career by becoming one of the first openly gay members of Congress. He was formally reprimanded by the House in 1990 for allegations of political impropriety relating to his association with a male prostitute.
Frank's current district -- which extends from the affluent, liberal Boston suburbs of Newton and Brookline to the cities of New Bedford and Fall River -- is considered safe Democratic political terrain. Frank did, however, receive an unusually strong challenge from Republican Sean Bielat in 2010.
Frank ultimately defeated Bielat, 54% to 43%.