Perhaps it was Mondragon? Mondragon started in 1956 and is now at 80000 workers and an annual revenue of 14 billion. It's still a worker cooperative in the 21st century, though :)
Not a US company or established in the US. So not the example I asked for. I am aware of other non-US cooperatives, eg. http://en.m.wikipedia.org/wiki/Amul
There was a company, a big one, that I forget the name of that was run like that through the second half of the 20th century, but I can't remember the name :(