NEW YORK -- In its latest momentous policy shift, the Boy Scouts of America will admit girls into the Cub Scouts starting next year and establish a new program for older girls based on the Boy Scout curriculum that enables them to aspire to the coveted Eagle Scout rank.

Founded in 1910 and long considered a bastion of tradition, the Boy Scouts have undergone major changes in the past five years, agreeing to accept openly gay youth members and adult volunteers, as well as transgender boys.

The expansion of girls' participation, announced Wednesday after unanimous approval by the organization's board of directors, is arguably the biggest change yet, potentially opening the way for hundreds of thousands of girls to join.

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CBS News' Jim Axelrod met 16-year-old Sydney Ireland -- who's been an unofficial member of her brother's troop since she was 4. She wanted to become an Eagle Scout just like her brother.

"Not every girl has to want to do the things that the Girl Scouts do," she told CBS News. "I don't -- I want to do the things that the Boy Scouts do."

A Boy Scout works on a canoe at camp Maple Dell on July 31, 2015, outside Payson, Utah. Getty

Many scouting organizations in other countries already allow both genders and use gender-free names such as Scouts Canada. But for now, the Boy Scout label will remain.

"There are no plans to change our name at this time," spokeswoman Effie Delimarkos said in an email.

Under the new plan, Cub Scout dens -- the smallest unit -- will be single-gender, either all-boys or all-girls. The larger Cub Scout packs will have the option to remain single gender or welcome both genders. The program for older girls is expected to start in 2019 and will enable girls to earn the same Eagle Scout rank that has been attained by astronauts, admirals, senators and other luminaries.

Boy Scout leaders said the change was needed to provide more options for parents.

"The values of scouting -- trustworthy, loyal, helpful, kind, brave and reverent, for example -- are important for both young men and women," said Michael Surbaugh, chief scout executive.

The announcement follows many months of outreach by the BSA, which distributed videos and held meetings to discuss possibility expanding girls' participation beyond existing programs, such as Venturing, Exploring and Sea Scouts.

Surveys conducted by the Boy Scouts showed strong support for the change among parents not currently connected to the scouts, including Hispanic and Asian families that the BSA has been trying to attract. Among families already in the scouting community, the biggest worry, according to Surbaugh, was that the positive aspects of single-sex comradeship might be jeopardized.

"We'll make sure those environments are protected," he said. "What we're presenting is a fairly unique hybrid model."

During the outreach, some parents expressed concern about possible problems related to overnight camping trips. Surbaugh said there would continue to be a ban on mixed-gender overnight outings for scouts ages 11 to 14. Cub Scout camping trips, he noted, were usually family affairs with less need for rigid polices.

The Girl Scouts of the USA have criticized the initiative, saying it strains the century-old bond between the two organizations. Girl Scout officials have suggested the BSA's move was driven partly by a need to boost revenue, and they contended there is fiscal stress in part because of past settlements paid by the BSA in sex-abuse cases.

In August, the president of the Girl Scouts, Kathy Hopinkah Hannan, accused the Boy Scouts of seeking to covertly recruit girls into their programs while disparaging the Girl Scouts' operations. On Monday, Latino civic leader Charles Garcia, just days after being named to the Girl Scouts' national board, wrote an opinion piece for the Huffington Post calling the BSA's overture to girls "a terrible idea."

"The Boy Scouts' house is on fire," Garcia wrote. "Instead of addressing systemic issues of continuing sexual assault, financial mismanagement and deficient programming, BSA's senior management wants to add an accelerant to the house fire by recruiting girls."

Instead of recruiting girls, Garcia said the BSA should focus on attracting more black, Latino and Asian boys - particularly those from low-income households.

The BSA recently increased its annual membership fee for youth members and adult volunteers from $24 to $33, but Surbaugh said the decision to expand programming for girls was not driven by financial factors. He expressed enthusiasm at the possibility that the changes could draw hundreds of thousands more girls into BSA ranks over the coming years.

The Girl Scouts, founded in 1912, and the BSA are among several major youth organizations in the U.S. experiencing sharp drops in membership in recent years. Reasons include competition from sports leagues, a perception by some families that they are old-fashioned and busy family schedules.

As of March, the Girl Scouts reported more than 1.5 million youth members and 749,000 adult members, down from just over 2 million youth members and about 800,000 adult members in 2014. The Boy Scouts say current youth participation is about 2.35 million, down from 2.6 million in 2013 and more than 4 million in peak years of the past.

Earlier this year, the National Organization for Women urged the Boy Scouts to allow girls to join. NOW said it was inspired by the efforts of a 15-year-old New York City girl, Sydney Ireland, to emulate her older brother, who is an Eagle Scout.

Unlike the Boy Scouts, the Girl Scouts have maintained girls-only status for all their programs. The empowerment of girls is at the core of its mission.

"We know that girls learn best in an all-girl, girl-led environment," said Andrea Bastiani Archibald, a psychologist who provides expertise on development for the Girl Scouts' national programming.

The Boy Scouts' new policy on girls was hailed by Zach Wahls, an Eagle Scout who played an active role in pressuring the BSA to end its ban on gays. However, he urged the Boy Scouts to take one more step and end its exclusion of atheists and non-believers who do not profess a "duty to God."