For reference, last year Golden State had 500,000 at their parade.
Just curious, drinking in public is not common/forbidden in the States, right? I just noticed that no one is really having any beer cans in their hand or such. I just know those parades from my hometown soccer team Borussia Dortmund and everybody would drink beer after beer at the championship parade. Drinking in public is very common and legal here in Germany. But for safety reasons, it's propably better not to have 1 Million drunk people ;-)