Start with the state government website, which you can find using the State Legislative Websites Directory. For a multi-state or all state comparison, use HeinOnline National Survey of State Laws or Nexis Uni. These sources can also be used to search for regulations or administrative codes and cases. For a comparison of state bills, try the National Conference of State Legislatures bill tracking database first.
Look up a state manual or "blue book." For an internet search, be aware that a state or city may use several domains (gov, us, edu, org, com). Look up the domains at Search government URL. The American Library Association State Agency Database Project lists state depository library programs. For older state publications, use HOLLIS to get Monthly Checklist of State Publications.
For additional sources, visit the Harvard Law School Comparing State Laws and Constitutions research guide.
Code & Ordinances
There is no easy way to search all municipal codes at the same time. This HKS Library Fast Answer provides detailed instructions for locating municipal ordinances or codes in Nexis Uni. Please note that major metropolitan areas may have town, city and/or county ordinances that apply depending on what part of the metropolitan area you are researching. In some areas, you may have county and city codes that apply.
Search for reputable NGOs and think tanks in your policy area as they may have expert practioners that monitor changes to state and local code.
Other free resources that provide access to ordinances/codes are listed below: