It's not Fontana, but it's (not) close - Fiddler's Grove

Certain music is regional, and although you'll find the exceptions - I'm sure there is an excellent hip-hop artist in Bozeman, Montana - most talent for particular musical genres tends to be localized.

Take bluegrass. Years and years ago I attended a bluegrass concert in Fontana, California, but if you really want to find bluegrass music, you don't go to Fontana. You'd have better luck in, say, Leesburg Virginia. And even the people from Leesburg go to Union Grove, North Carolina:

“First contest, first first-place,” said Brennen Ernst, a 15-year-old banjo player from Leesburg, Va., minutes after picking up a blue ribbon at the 85th annual Ole Time Fiddler’s and Bluegrass Festival in Union Grove, N.C. It was afternoon on the festival’s second day, and Brennen, wearing a black derby and a pink T-shirt, had been playing all but nonstop since before the festival opened....

Brennen wasn’t the best musician I heard over four days at the festival, known to most simply as Fiddler’s Grove, but it was clear that he was off and running, caught in an obsession on display around the 45 acres of rolling hills at the festival site. Countless string-band jam sessions ebbed and flowed from the morning’s first rooster crow until late at night, when a sequined blanket of stars draped the blue-black sky.

And Fiddler's Grove isn't even the largest festival:

Old-time and bluegrass music festivals have become a summer ritual all around the country, but nowhere is the experience quite the same as in the Southern Appalachians, the music’s birthplace. Popular events in Galax, Va.; Mount Airy, N.C.; and Clifftop, W.Va., draw zealous fans and gifted musicians. Fiddler’s Grove may not be the largest or best known of the major festivals, but its claim to fame is that it’s the oldest continuously held one.

More at the New York Times, including a brief account of a family feud between two descendents of festival founder H. P. Van Hoy, which resulted in two competing festivals. (Sounds like the Indy war, except this is in the NASCAR world.)