do mike and frank fritz on american pickers actually drive across country or is their van shipped to their destination

According to the New York Times, they actually drive across the country; in fact that's part of how they find their "rusty gold," as Mike Wolfe puts it.

He and Frank Fritz drive the back roads of the country in search of old signage, gasoline pumps, bicycles, and other treasures.

Wolfe even tells a story about finding a classified ad for an antique motorcycle, “I drove all the way to New York, slept in the guy’s driveway and knocked on his door the next morning.” Wolfe valued the bike at around $55,000 and bought it for $25,000.

While the boys are traveling around the country, the female member of "Pickers," Danielle Colby, has just opened a new shop in Chicago; a boutique on North Avenue called 4 Miles 2 Memphis.