Promoting the Airstream "Overlander" trailer at the end of the 1950s, this advertisement proclaims, "When you own an Airstream, you know���_and the world knows���_you own the finest travel trailer built." At 26 feet, accommodating six people, and equipped with a kitchen, shower, and bathtub, this was one of the largest trailers Airstream built. The company promoted this model as a "home away from home" for those with a restless spirit of adventure. First developed in the late 1930s, the Airstream trailer became especially popular after World War II, when sales were fueled by postwar prosperity. As Americans earned more money and had more time for leisure, they began taking more vacations, traveling mostly by car. Vacation travel accounted for roughly one-quarter of all driving in the entire country, and hundreds of thousands of freshly paved roads invited Americans to drive farther than ever before. By the end of the decade, nearly half of all American families took long vacation trips of 600 miles or more every year.