If an electric rail line using less-then-full-size railcars connects a series of towns, suburban or not, on its own RoW (could include some street-running) then it sounds like the modern equivalent of an interurban. I did not get to ride any thing beyond the CA&E, but it was considered an interurban and matches those criteria. Lucky Dave!!
But if you want, you can still ride the CSS&SB, perhaps writing for permission to ride the front platfrom sradning across from the engineer, after finding some legitimate excuse for them to give you permission. And you can ride St. Louis light rail and relive the Ilinoise Terminal subway and bridge exit from St. Louis and realize on the trip though and past Bellville what a classic interurban was like.
I think I am lucky to Hsve Jerualem Light Rail to ride, and there is one area, on the northern section of the line, between Sufat and Pizgat Zeve, where the side-of-road operation resembles an interurban line, the most scenic portion.