It's a milestone we haven't seen in a long time... 20 years, to be exact. For the first time in two decades, General Motors (NYSE:GM), Ford (NYSE:F) and Chrysler all gained market share in the U.S. in the first half of 2013.

It's proof that the Detroit renaissance is for real, but can the Big Three keep it up? In this video, Fool.com contributor John Rosevear looks at what's driving the American auto sales boom and ponders why Detroit's winning streak may be at risk.

Fool contributor John Rosevear owns shares of Ford and General Motors. Follow him on Twitter at @jrosevear. The Motley Fool recommends Ford and General Motors. The Motley Fool owns shares of Ford. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.