The regional data could be found in this resoruce. Percentage of households that owned dogs, number of dog-owning households, mean number of dogs per household and total dog population by region and state, Dec. 31, 2006 U.S. Pet Ownership & Demographics Sourcebook (2007 Edition) http://www.avma.org/reference/marketstats/sourcebook.asp
I’m doing research for a presentation that involves dogs and I came accross this web site www.hsus.org/pets/issues And there are approximately 74.8 million dogs owned in the United States as far as certain regions I don’t know.