The following directory is provided as a starting point.
When making contact with your States Department of Business / Labor
make sure to explain Your Trade and Location.
All contractors are treated differently within every State.
You can expect Plumbing, Electrical and any Health related contractor such as asbestos abatement or pesticides to go under strict guidelines both in the application and on going business process.
If you are an out of State Contractor there will be special requirements.
Alabama
http://www.genconbd.state.al.us/
Alaska
http://www.alaska.net/~achp/
Arizona
http://www.rc.state.az.us/
Arkansas
http://www.state.ar.us/clb/
California
http://www.cslb.ca.gov/
Colorado
http://www.dora.state.co.us/
General Contractors …