When the Red Sox came to Nats Park two summers ago, the estimate was that something like 65 or 75 percent of the packed stands were filled with Red Sox fans. It was an unforgettable atmosphere, filled with jarring accents, green t-shirts and the unaccustomed whiff of a fan base that expects to win.

And if there were that many tens of thousands of local Red Sox fans just thirsting for some Red Sox action in D.C., it stands to reason that someone would eventually find a way to tap into that market, even in summers when the Red Sox don’t visit the area.

And thus, welcome to the first day of the first year of Red Sox Camp — the official summer camps of the Boston Red Sox — in, yes, Bethesda. It’s believed to be the first team-branded MLB camp outside of a team’s home market. The camp was open for up to 125 kids ages 5-13; it sold out. In, yes, Bethesda.

“Obviously it’s a loyal group of people, and they’ll travel far and wide to touch anything that has Red Sox on it,” said Brendan Sullivan, the co-founder and executive director of Red Sox Camps, which is doing nine sessions of camps featuring 1,000 campers in Boston, in addition to this current week at the Norwood School in Montgomery County. “There are very few teams that have the fan base to do this. Kids cling to the message a little bit more when you’ve got Boston Red Sox across your chest, and we’re taking advantage of that.

And thus, the Bethesda campers all receive a “soup to nuts” Red Sox uniform, complete with stirrups and pants, belts and jersey. The coaches — about half of whom came down from the Boston area for the week — all wear Red Sox apparel. Many of the families pull up in cars covered with Red Sox stuff, and parents sit in the stands wearing Red Sox hats. The campers will also be taking a trip to Camden Yards on Tuesday, where they’ll get a VIP tour and meet with Dustin Pedroia.

“We knew that this would be successful eventually, but it’s been wildly successful,” Sullivan told me. “The Red Sox see what this could do to engage their young fans, and that’s made it very successful.”

Now, Sullivan, I should point out, is a D.C. guy. He was born and raised in the District, went to St. Albans , and is the co-founder and executive director of Headfirst Camps, a D.C. company that provides baseball camps across the country. That’s part of the reason the Red Sox outreach began here, and that also makes him, yes, a Nats fan.

“Not only a Nationals fan, but a Nationals season ticket holder,” said Sullivan, who played at Stanford and then in the Padres organization. “The Nationals fan in me hopes and trusts that this’ll start to happen here, that you’ll have the same type of fanaticism about the Nats one day. ”

Maybe so. Indeed, a few kids have actually shown up to the first-ever D.C. Red Sox camp in Ryan Zimmerman tees, although it’s unclear whether any of them gave cold and icy stares to their Red Sox-wearing peers. Sullivan said around two-thirds of the Major League clubs don’t even run branded youth camps in their own markets, and that he thinks they’re missing out on a chance to engage youth and form life-long allegiances. In the meantime, the plan is for Red Sox Camps to continue to branch out, to other parts of New England and to other parts of the country that, like D.C., are filled with Red Sox fans.

“Folks are looking for a good baseball experience, and when they see the Red Sox name, people assume quality,” he said. This is not something we’re trying to do in the face of the Nats. I’m a Nats fan, I go all the time. For us, this is something that every Major League team, especially those that are trying to grow a fan base, should do.”