All 50 states have some case law online for some period of time. The best collections, offered by about 10 states, consist of case law that dates from 1986-1992 to the present. Another group of about 20 states have cases since they began Web pages, so about 1995-1996 to the present. Lastly, there are about 15 states with only advance sheets or recent case law online. The cases are posted for a month or two, then deleted.
Several states have more than one source for case law.
Only Oklahoma offers case law going back several decades, and is the best court Web site in the United States. Findlaw has begun to archive all court opinions, so the body of case law will continue to grow even for those states that delete their opinions after a few months. I was just counting the free sources. All fifty states have posted the text of their constitution and almost all states have their statutes and pending bills online for free. Arizona Supreme Court opinions since Dec. 1997 Court of Appeals, Div.