“Our camp base is shrinking,’’ says Larry Levy, chairman of the America’s Camp Foundation. “And it’s extraordinarily hard to raise money for 9/11 causes 10 years out.’’ The camp is funded through private and public donations. Campers pay nothing.

At the outset, the camp’s founders - all veteran camp owners - committed to 10 years, but left open the possibility of extending it. Now the children are growing up and aging out. Many of the original campers are in their 20s and have become counselors.

Each August, many of the children return for a week. They have laughed, cried, and formed close bonds. During the year, many keep up with one another and arrange get-togethers. Some say they consider camp a second home, their fellow campers and the counselors a second family.

“It’s been funny meeting kids who are the same age now as I was when it happened,’’ she says. “They didn’t know their parent, but they’ve grown up with a sense of exactly what happened.’’

Seventy-eight children showed up that first summer. Later the camp welcomed a handful of children of police officers and firefighters killed in the line of duty during the past decade. This year there are 170 campers between ages 7 and 15 - and 105 former campers who are now counselors or counselors in training.

Michelle was 11, Robert was 9, when their father, Joseph, died in the World Trade Center, where he was attending a business meeting. The following summer, America’s Camp opened. The idea was to give children who had lost a parent in the terrorist attacks a haven where they could escape the grief and curiosity that dogged them.

Some campers note that they’ve known their friends at America’s Camp longer than they knew their lost parent.

“The friends you make here,’’ says Michelle Mathai, a senior at Colby College, “have an understanding of each other no one else has. And it’s the first time people treated us as normal kids.’’

Mathai and his sister, Michelle, 21, started coming to this idyllic camp in the Berkshires as bewildered campers in the summer of 2002, joining other children who had lost parents in the attacks. But this is the last time they’ll be here. Today the camp closes for good, having fulfilled its 10-year mission.

“They’re all good kids,’’ says Mathai, a Tufts University freshman from Arlington. “It’s about them and making sure that they have fun.’’

PERU, Mass. - Robert Mathai is headed to a game of “garbage ball’’ - which he describes as “a combination of football, soccer, handball, lacrosse, and a free-for all’’ - with other youths who lost parents in the terrorist attacks of Sept. 11, 2001. At 18, he’s moved from camper to counselor at America’s Camp.

For the past five years, America’s Camp has been held on the sprawling grounds of Camp Danbee, owned by Jay Toporoff, who donates its use. At the end of last year’s session, he and the other directors of America’s Camp broke the news that 2011 would be its final year.

“It’s bittersweet,’’ Toporoff says. “But we all know it’s time.’’

For Julia Coombs of Abington, her last session at camp is both fun and sad. She is thrilled to be here but says she and her friends are “devastated.’’ There are five of them who have bunked together for nine years, and they’re like sisters. All are counselors this summer.

“We’re all so close we hate leaving each other,’’ says Coombs, who was 8 when her father, Jeff, was killed on American Airlines Flight 11, which crashed into the North Tower of the World Trade Center. “People are saying the hardest thing in their lives was 9/11 and the second hardest thing is losing America’s Camp.’’

The fact that camp is closing around the 10th anniversary of the attacks is, to some, a double whammy. “It’s all crashing down in one month,’’ says Coombs. “It’s a lot to take in.’’

Robert Mathai says some of the children fear that Sept. 11 will recede from people’s memories. “It’s not something you need to be reminded of every day,’’ he says. “But we don’t want people to forget what happened. We are trying to find the middle ground here.’’

Art has been one of the hallmarks of America’s Camp; each year there is a project memorializing Sept. 11. Some of the artwork is in the Norman Rockwell Museum in Stockbridge, and some of it is in the new “memory hall’’ at camp. From the ceiling hangs a red, white, and blue quilt, with patches sewn by the campers. A totem pole stands in one corner, covered with felt and paper scenes. This year, campers and counselors are making ceramic tiles. Some of the artwork will be donated to the National September 11 Memorial & Museum at ground zero.

For many children, the raw grief of losing a parent has evolved into painful acceptance, where many speak proudly of their mothers and fathers.

Anna Sweeney of Acton was 5 and her brother, Jack, was 4 when their mother died. Amy Sweeney, a flight attendant on Flight 11, has been hailed as a hero for calling in crucial details of the hijackers to ground crew. Each year an award in her name is given to an individual who shows uncommon courage.