Already compiled surveys of state law provide you with an easy-to-navigate guide to laws in a particular area across all fifty states. Using surveys saves you from having to do the initial research yourself; all you're left with is updating. The need to search for laws in each and every state is eliminated. Multi-jurisdictional surveys are available in Lexis, on Westlaw, and in print.
Multi-jurisdictional surveys can be helpful for a legal argument by demonstrating that there is consensus among the states on an issue of law.
Surveys are available in print, on Lexis Advance, Westlaw Next, Hein Online, and several trustworthy websites. (Direct links are provided, as well as instructions to find these resources on your own.)
On WestlawNext, simply type "50 State Surveys" into the main search box. Once selected, it will take you to a page breaking down both statutory and regulatory surveys according to topic. You can search for particular surveys using the main search bar.
On LexisAdvance, click on Browse Sources and type "50 State Surveys" into the sources search box. Click on "view table of contents" to see the entire list of subjects and search within it.
HeinOnline has a database called "Subject Compilations of State Laws." This enormously useful database contains state surveys on hundreds of subjects in a variety of formats. To access it, start from the library's homepage, click "Law School Databases," select "HeinOnline," and when brought to HeinOnline's main page, select "Subject Compilations of State Laws" and then databases. You can search the entire database, or browse by subject. Here's a guide for searching this database.