If yes, then when was Stack Overflow proposed on Area51? And who proposed it? I think it is the most active site in the Stack Exchange network.
Stack Overflow, Server Fault and Super User (collectively "The Trilogy") were the first three sites in the StackExchange Network and came before Area51. Once The Trilogy was successful (and after a brief foray into a paid SaaS model) we created Area 51 to democratically determine the subjects for the next Q&A sites to add to the network.
Stack Overflow is the most active site by far - see http://stackexchange.com/sites for detail:
- Stack Overflow 2.3 million questions
- Super User 103 thousand questions
- Server Fault 98 thousand questions
So to answer your headline quetion - No.