FREEPORT — For two people who have been living in a motor home for the past two decades, Diane and George Gravlee sure like to build houses for other people.

“We’re living in 300 square feet but building simple, 1,300-square-foot homes for others,” Diane Gravlee said last week.

Diane and George Gravlee, ages 71 and 74, respectively, have been traveling across the country in a recreation vehicle on a mission to work with Habitat for Humanity in every state. Last week, they checked Maine off their list as their 46th state.

The Gravlees work through a Habitat program called Care-A-Vanner. Although Habitat for Humanity of Greater Portland doesn’t have a Care-A-Vanner program, the couple decided to come anyway.

“There was no way we’d get all the states checked off unless we just said we were coming,” Diane Gravlee said.

Laura Duplissis, Habitat volunteer and communications manager, said the Gravlees inspired the other workers and that it was helpful to have them at the Hummingbird Lane build site. The Gravlees were in Freeport from July 21-30.

“Beyond the fact that they’re really experienced, it’s a great experience for us to hear their stories,” Duplissis said.

The Gravlees definitely have acquired some stories during their 21 years of service.

The pair’s first build was in 1993 in Hawaii, although it wasn’t connected to Care-A-Vanner. They said they arrived hoping to have a vacation while also doing some volunteer work, and ended up falling in love with Habitat.

“We had a great time and decided this is what we’d do when we retired,” George Gravlee said.

After finding Care-A-Vanner, they decided to make it their mission to work in all 50 states. They hope to be done next year.

Prior to retirement, Diane was a librarian and George was a hydrologist. They said working with Habitat has given them new skills.

“We’ve learned how to build a house,” Diane Gravlee said. “We couldn’t do that before.”

But the Gravlees also said they’ve gotten a lot more than carpentry skills out of the experience.

“People say it’s a sacrifice; it’s not a sacrifice,” Diane Gravlee said. “We’re getting more out of this than we’re actually giving. At least, that’s how we think about it.”

They said they enjoy connecting with families and being able to help provide them with a home.

“It’s the kids that it has an impact on more than the adults,” George Gravlee said. “It molds their futures.”

The Gravlees have worked on some build sites multiple times. Although they’ve now been to 46 states, Freeport was their 135th stop.

The Gravlees said living out of an RV is no different from living in a house and while traveling, they go to local grocery stores, post offices, laundry centers and churches.

The Gravlees have a permanent home in South Carolina, where they live for about three months each year. They said they usually head home for fall and early winter.

After Freeport, the Gravlees are headed to New Hampshire. In September, they will check off Maryland and Delaware. Last on their list is North Dakota, which they hope to visit next summer.

Once they have been to all 50 states, their mission will be complete, but Diane said it won’t be the end of their work with Habitat.

“Someone asked if then we’ll stop doing this,” she said, “and the answer is no.”