The first Ohio State League played in 1887 before changing names to the Tri-State League.
The first 20th century Ohio State League started in 1908 as a class D loop and ran through 1916. Another Ohio State League was formed in 1936 and ran through 1947 except for a break in '42-'43 due to World War II. In 1945 the OSL was one of just four class D circuits in operation, yet it was one of the first of dozens of leagues to collapse after World War II. The class D Ohio-Indiana League was formed in 1948 with eight teams, with seven of the eight cities coming from the the Ohio State League. Six teams made their home in Ohio and the remaining two where from Indiana. This league lasted through 1951.