Historical state case law is available in the Trinity Series, three titles of significance to researchers of American legal history.
American Decisions: Cases of General Value and Authority Decided in the Courts of Several States (1910-1911)
An overview of 15,800 cases decided by various state courts from 1760 to 1869.
American Reports: Containing All Decisions of General Interest Decided in the Courts of Last Resort of the Several States (1912)
Containing 9,300 cases decided by various state courts from 1870-1887.
American State Reports: Containing the Cases of General Value and Authority Subsequent to Those Contained in the American Decisions and the American Reports Decided in the Courts of Last Resort of the Several States (1888-1911)
An overview of 20,500 cases decided by the state courts from 1888 to 1911.