As you may already know, Google Scholar offers an excellent collection of free federal and state case law for the following years of coverage.
Sup. Ct. pre 1776?
Fed. Circ. Cts. 1924?
Fed. District Cts. varies
States vary (most mid 1950s?)
Using the advanced search page, you’ve always been able to limit your search to a particular state, but now users may limit to specific courts and jurisdictions. You can even mix and match your selections.
Source: Robert Ambrogi’s LawSites