I hate to say it but New Jersey per capita is the best track state. The depth is solid and the state's population isn't close to others. I think its because NJ is located between two major cities (NYC and Philly) which makes for a highly competitive environment. Plus there is a lot of wealth and minor cities which equate to strong track programs and funding.
The past few years NJ could hang with California in the distance races as a whole and their sprint and field guys are very solid.
Forgot to mention everyone in NJ has an inferiority complex. I would know because I am from there.
I must admit the region which provides the best distance runners is the Midwest. The winters suck there and the summers suck there. The summers are muggy in NJ but the winters aren't so bad.