I entered the Dougan Creek Campground in southern Washington by hairpin switchbacks and dirt roads so narrow my sideview mirrors brushed foliage. As I wound through the grounds without cell service, I was on the lookout for a white school bus called the Bus Code, named for the samurai code of honor called bushido. Campers lounged under R.V. awnings and played cards at picnic tables. The Bus Code sat parked across from an outhouse swarming with flies. I pulled up, mistaking the tinted windows to mean the family wasn't home until Danny Mulvihill poked his head through one of the top panes. "Come on in," he said.

The Bus Code was long and dim, with two very bright bulbs on the ceiling that looked like interrogation lights. Behind the driver's seat, an unlit wood stove spanned the width of a large lounge chair. A stuffed bear slumped on the kitchen counter and a hodgepodge of produce—a bunch of bananas, one pepper, a loose orange, and a bag of lettuce—hung from a metal rack. Farther back, a broken washer and dryer were being used for storage beside a bunk bed, a compostable toilet, and a wooden frame that would one day be a shower, but which for now was where the dog slept. The Bus Code had little decor. There was a wall tapestry in the bathroom with a poem by the Dalai Lama, souvenir fridge magnets shaped like palm trees and Hawaiian shirts, and a skateboard over the windshield that said "Skate Free."

Less than a year after they bought a house in Spokane to settle down with their two young daughters, Danny and his wife, Alex, got bored. Danny hated his job. Alex couldn't bear the months of rain. The couple, who married five months after meeting at a hostel in Mexico, preferred to travel, live spontaneously, and reside in warm places. They've lived in Reno, Austin, Ecuador, Peru, West Palm Beach, and Santiago. One day, they came upon bus conversion videos on YouTube featuring families talking about air hoses and wanderlust and couches that turn down into beds. Convinced that becoming skoolies—people who live mobile lives in converted school buses—would afford them freedom and adventure, they sprung for a white 36-foot 1995 Thomas Built Saf-T-Liner for $4,500. They spent about $20,000 and seven cold Northwestern months converting the Bus Code. They pulled their older daughter, Amaia, from kindergarten and, last June, rented out their house. In the first three months they lived in the Bus Code, they hopscotched from campsite to campsite across Washington using a $35 yearly Discover Pass, which allowed them to stay in state parks at no additional cost. In 55 days, they spent zero money on lodging. (They did have to sleep in a Home Depot parking lot one night when all the nearby campsites were full.)