There are a growing number of biergartens around the U.S. I can think of three or four that have opened in the past year or less in the Washington, D.C. area where I reside. I worry a bit that it may become somewhat faddish.

One of the consumer magazines covering beer and brewing (I think it's Draft but I don't remember with 100% certainty who I heard was doing the research) has a reporter working on a piece about American biergartens for their September issue.