A 1970 Michigan festival that pulled 200,000 to 300,000 fans to see the likes of the MC5, the Stooges, Mitch Ryder and blow-ins Rod Stewart and Joe Cocker? It happened although there's little about it in the history books, save David A. Carson's excellent Detroit rock retrospective "Grit, Noise and Revolution".
Goose Lake was a wild gathering by all accounts, with acid and harder stuff openly on sale and nobody seeming to remember WTF occurred. We do know a wasted Dave Alexander played his last show with the Stooges, Iggy firing him for being too out of it. You read that last sentence correctly.
A three-day festival that drew 300,000? That's big by any measure. These days they'd claims the same turn-out for a vigil for Michael jackson. The Metro Times has redressed the lack of coverage 38 years later with an excellent piece on the three-day extravaganza. Read it here.