The State Archaeologist Office in each state is an excellent source of information about archaeological sites or cultures. According to US federal law, each state must have a State Archaeologist office, established by the state to oversee the compliance with historic and prehistoric burial laws and (in some cases) over see Section 106 compliance and maintain archaeological collections produced by those investigations.
If you are a working archaeologist in the state, you can almost certainly obtain access to the records, articles, reports, artifact collections and maps kept at the State Archaeologist office; but these are not always open to the general public. It won't hurt to ask; and many of the records are open to students. The University of Iowa maintains a list of National Association of State Archaeologist's Offices.
