Route 84 was established in 1923 and originally ran from south of
Madison to west of
Andover along the current alignment of
State Route 307; from south of Madison to Dorset; and from Dorset to West Andover. It was expanded in 1926 to
Willoughby Hills along a previously unnumbered road. In 1931, the route was truncated at Dorset and Dorset to West Andover was decertified. In 1935, Route 84 was rerouted from Madison to
Ashtabula along the previous State Route 307 alignment, which was unnumbered before 1933. The former alignment from south of Madison to Dorset was certified as State Route 307. In 1938, it was extended to the
Pennsylvania state line along the former alignment of
State Route 83 from Ashtabula to Kelloggsville, which was unnumbered before 1926, and along a previously unnumbered road from Kelloggsville to the state line. ==Major junctions==