Ohio State Route 421 is essentially the business alternative to US Route 42 and US Route 224 in Lodi, Ohio. Both ends of Ohio Route 421 are points where US Route 224 joins US Route 42's expressway bypass around the north side of Lodi. The western beginning of Ohio Route 421 is the eastern continuation of the road US Route 224 used to come into the area from the west. But as US Route 224 joins US Route 42 north at this point, the eastward road into Lodi is left to its own devices. So that road calls itself Ohio Route 421, and it serves Lodi because neither of the US routes will! In the center of Lodi, Ohio Route 421 crosses Ohio Route 83. But that's the only numbered highway Ohio Route 421 will encounter until it leaves town toward the northeast and ends. The far end is where US Route 224 resumes its eastward journey, exiting from US Route 42. I'm not sure why Ohio Route 421 ends in "21", when usually the routes in the 400's and 800's are numbered with the last two digits matching the two-digit highway serving as their respective namesakes; in other words, "421" ought to be named after a highway "21". I don't believe US Route 21 ever came through here. I would have expected it to be numbered "442" or "842", in reference to US Route 42, which it replaces. But maybe the first two digits match the two digits of "42", so that was the reasoning for the number "421".
My photo of Ohio Route 421 shows the guide marker seen by those heading northward on Ohio Route 83 in downtown Lodi. The signage here faces south on the northwest corner of the dodgy intersection, where both routes bend at their common point. This photo was taken at the end of a long day driving around northeastern Ohio in October 2022.