Bullhead City, Arizona. 123 teams playing Saturday and Sunday, 3-4 games each. It's called the River Daze (as it is adjacent to and in view of the Colorado River and a bit hot). It's our 6th official year, 10th unofficial (a friend and I started it with 4 local kid teams 10 years ago; it's been growing every year). All the referees are volunteers. The proceeds go to park improvements (we have 40 acres under lights but have another 20 acres that need field lights).
Simultaneously at the same park, the Rotary Club runs the Burro BBQ (it's 67th year), the River Cruizers do a free classic car show, the Habitat for Humanity does a construction project to raise money for it's next home project, and there is a water slide and amusement area for the younger kids. There are 11 casinos across the river in Laughlin and shows which run every evening (Billy Bob Thornton's band is playing this weekend, in addition to the Voodoo Cowboys, a variety of cover bands, some comedy and burlesque shows). It makes for an attractive venue for parents who want to let their kids play during the day but want to socialize at night.
I think it will only grow bigger as the years go on (we had about 90 teams last year).