The Ford F-150, shown here in Limited trim, and its Super Duty siblings are America's top-selling pickups. Photo credit: Ford Motor Co.

June was the best month for U.S. auto sales since 2007, and one big factor is the boom in sales of full-sized pickup trucks. Ford (F -0.45%), General Motors (GM 0.32%), and Chrysler all posted big gains in pickup sales last month, and all three gained U.S. market share in the first half of 2013 – the first time that has happened in 20 years.

What's behind the boom? In this video, Fool.com contributor John Rosevear looks at the economic "perfect storm" that has made for great pickup sales, and at why that's likely to be a big deal when the Detroit automakers report second-quarter earnings later this month.