According to the CMP Group's Game Developer Census, 39,700 people are involved in game development or publishing in the US, with another 8,100 in Canada.
Nearly half (46%) of the Americans in the industry are located in California (gee, there's a surprise), with just over 11% in Washington, and slightly over 7% in Texas.
Now, these numbers don't include everyone in gaming--services like outside PR, marketing, legal, and game tools companies are all excluded from these numbers. The census estimates that those groups comprise another 15,000, and plan to do further research at a later date.
Game Developer Research Debuts 2007 Census [Gamasutra]
