I am pretty sure they were D-II in the 1980s, but I have no way to confirm it either way. At some point in the 1990s they dropped down, because I know they weren't in the same division as Canfield from the mid 90s until present with the exception of 2019-2021. Canfield was D-III in the 1980s and AA back in the days of only 3 divisions. I don't know if Steubenville was AA or AAA, perhaps one of their posters can let us know. Canfield started gaining enrollment/population in the mid 1980s going from a small D-III school to a mid size D-II school by the early 2000s. Canfield also went from being a very rural/ farm community and enrollment to having mostly students from houses in town.
Steubenville conversely started heading in the opposite direction in the late 80s into the early 90s and losing population and enrollment, or even holding steady while many schools in Ohio were growing.