GRAND FORKS-Diane Gravlee once heard that 20 percent of the human population has a specific gene that makes people more restless and curious.
She and her husband, George, related to the idea-their urge to explore has taken them to every state in the U.S. since 1993 in an effort to build homes through Habitat For Humanity.
"We decided we had that (restless) gene," Diane Gravlee said. "Other people at home would ask, 'How can you just leave your house and go off?' "
This week, with North Dakota marking the couple's last state, they're helping the Red River Valley Habitat For Humanity build a house in Grand Forks.
The Gravlees sold their home in 1999 and, until 2005, only lived in an RV that they drove from state to state for 10 months of the year. The Gravlees typically traveled with other RV-driving Habitat For Humanity volunteers through the organization's nationwide RV Care-A-Vanner program, working on "builds," as the houses are known.
They have since moved back to South Carolina to be closer to their family. But they still drive around about 40 percent of year-the Gravlees have worked on more than 138 different builds with more than 94 different Habitat For Humanity affiliates in 22 years.
"We've really liked traveling," George Gravlee said of the couple's journeys. "Another goal is to visit every national park and monument. And we've only hit around 300."
Red River Valley Habitat For Humanity doesn't usually bring in volunteers from outside the state, volunteer coordinator Mary Paas said. The Gravlees specifically called the Grand Forks affiliate to see if there were projects in their last state on which they could help.
Since Sunday, they have camped out at the Grand Forks campgrounds and have done work on the Habitat For Humanity site on South 24th Street.
"We've been blessed," Paas said. "They're very knowledgeable in construction, and they've really helped the volunteers from our community. Not all volunteers have done this before."
Volunteers for a separate organization are also passing through Grand Forks this week. Bike & Build participants bike cross-country and work on construction of affordable homes in the area. Students from universities such as Dartmouth, Texas A&M, Syracuse and the University of Virginia will arrive in Grand Forks today before moving on to Devils Lake Friday.
The Red River Valley Habitat For Humanity will also present the Gravlees with a recognition plaque today.
"It's a real accomplishment to go to all 50 states," Paas said. "We want to thank them for their dedication and perseverance."