The Boy Scouts of America will be fully inclusive for girls for the first time in its nearly 100-year history, its leaders announced Wednesday, the latest move to adapt the organization’s rules in an era of declining membership.

The organization said that its board unanimously approved the decision to allow girls into the Cub Scouts program, which will eventually allow them to earn the prestigious Eagle Scout ranking, after years of requests from families and girls themselves.

Deliberation over the plan had caused friction between the organization and the Girl Scouts of the USA, which spilled into public in August when a letter from Girl Scouts President Kathy Hopinkah Hannan accusing the Boy Scouts of trying to bolster dwindling numbers was released. The Girl Scouts have also seen its membership fall in recent years.

In a statement that does not mention the Boy Scouts, the Girl Scouts said they are “the best girl leadership organization in the world, created with and for girls,” adding that they are “here to stay.”

The Boy Scouts of America, which was the target of progressive ire over its decades-long resistance to changing rules that prohibited gay scouts and troop leaders, has made significant moves to open up its membership in recent years. The Boy Scouts ended the ban on openly gay scouts in 2013 and the prohibition on gay troop leaders in 2015. Earlier this year, the organization announced that it would allow transgender boys in its ranks.

Girls have been allowed to participate in some scouting programs at the Boy Scouts, but they have not been permitted to join the organization’s most popular programs, the Cub Scouts and the Boy Scouts, or earn the organization’s Eagle Scout ranking.

Chief Scout Executive Michael Surbaugh described the decision in part as an attempt to bring more families into the Boy Scouts, whose membership has declined by about a third since 2000.

“The values of Scouting — trustworthy, loyal, helpful, kind, brave and reverent, for example — are important for both young men and women,” he said in a statement Wednesday. “We strive to bring what our organization does best — developing character and leadership for young people — to as many families and youth as possible as we help shape the next generation of leaders.”

The company cited studies showing that cultural and economic factors made programs that could serve both boys and girls more appealing to modern families. The changes will begin in 2018, when girls will be able to enroll as Cub Scouts.

The Boy Scouts, founded in 1908 in Britain and in the United States two years later, has for decades been one of the country’s most prominent youth programs focused on character building, teamwork and outdoor skills.

Girls have been allowed to participate in the Exploring program, which focuses on teaching important career skills, since 1971. The co-ed Venturing program, about one-third of whose participants are women, split off from Exploring in 1998.

Still, some local troops have found ways around the national organization’s policies.

In Chevy Chase, Md., Boy Scout Troop 52 has been letting girls participate since 1997 as part of the co-ed Venture Scout crew. The women are unable to earn the organization’s rankings but can participate in the same activities, though they are technically part of a different program.

Ilana Knab wishes the changes came sooner for her family. For years, she has watched her daughters, now 14, 16 and 21, participate in the local program, with her oldest earning the Ranger award, the highest ranking a woman can achieve. But the 21-year-old never received the same recognition as her son, now 19, who earned the Eagle Scout title.

Attaining the status of Eagle Scout is considered a badge of honor that is recognized beyond the organization: It can help participants get into colleges and open the door to certain scholarships.

Knab’s 16-year-old daughter, Cassidy, who holds a leadership position in the group, said that distinction mattered.

“Eagle Scout gets them somewhere on their resume,” she said. “It will be amazing to say you got Eagle and people know what you’re talking about and know the work you put into it.”

A junior at Bethesda-Chevy Chase High School, Cassidy is “extremely happy” that women will have the opportunity to join the program at a younger age and work their way up to achieving Eagle Scout.

Will Stone, the Scoutmaster of Troop 52, said that having a co-ed program benefits both the girls and boys in his 70-person troop, 16 of whom are girls. Stone said they’ve been pushing for full inclusion.

“The young women who are part of the troop do all the hikes, they are deserving of the chance to earn the same rank advancements and deserving of a chance to stand in front of everyone and receive the Eagle,” Stone said. “They’re up for the challenge, and they’re ready to do this.”

The Boy Scouts’ relationship with its largest partner, the Mormon Church — about 20 percent of Scouts are Mormon — has grown increasingly fraught in the wake of recent changes. Earlier this year, the church announced that it would stop participating in two Boy Scouts programs for teenagers.

In July, a speech that Donald Trump delivered to thousands of Scouts — in which the president flouted the organization’s traditions by criticizing his opponents, gloating about his election victory and sharing stories about yacht parties — prompted its chief Scout executive to issue an apology.

Mary Hui contributed to this report.

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