Actually Whistler Blackcomb is one resort. It's two gigantic seperate mountains. They are building an ariel tramway that goes from one mountain to the other. Your lift ticket is good at both, Intrawest owns and runs them both, same base village, etc. With the new tramway, you can fairly easily ride both in the same day now. They could easily be two resorts though.
Whistler Blackcomb - Official Ski Resort Website - Whistler, BC, Canada
Seems to me it's pretty much like Winterpark/Maryjane. The two are often mistaken for two different resorts when it's actually all one resort. Granted, Whistler Blackcomb is like 10X the size of WM/MJ, much more committing terrain, etc.