The decision, which came after years of resistance and wrenching internal debate, was widely seen as a milestone for the Boy Scouts, a symbol of traditional America. More than 1,400 volunteer leaders from across the country voted, with more than 60 percent approving a measure that said no youth may be denied membership “on the basis of sexual orientation or preference alone.”

The top national leaders of the Boy Scouts, who pledge fealty to God and country, had urged the change in the face of vehement opposition from conservative parents and volunteers, some of whom said they would quit the organization. But the vote put the Scouts more in line with the swift rise in public acceptance of homosexuality, especially among younger parents who are essential to the future of an institution that has been losing members for decades.

The policy change, effective January 2014, is unlikely to bring peace to the Boy Scouts as they struggle to keep a foothold in a swirling cultural landscape, with renewed lobbying and debate already starting Thursday evening.

The Scouts did not consider the even more divisive question of whether to allow openly gay adults and leaders. This drew criticism from advocates for gay rights, who called the decision a breakthrough but vowed to continue pressing the Scouts to allow gay members of all ages.

Some conservative churches and parents said the Scouts were violating their oath to be “morally straight” and said they would drop out.

Still, for gay men who were forced out of scouting and for their allies, thousands of whom joined the push for change, the opening of membership was more than welcome.

“I’ve waited 13 years for this,” said Matt Comer, now 27, who had to leave his scout troop at 14 after he started a Gay-Straight Alliance at his school. Since the fourth grade, he said Thursday, he had dreamed of becoming an Eagle Scout and was crushed when he was denied the chance.