Columbus, Cincinnati and northeast Ohio
Taken together, Cleveland, Akron, Canton and Youngstown have more listings than any single Ohio city, all within about an hour of Akron. Youngstown's shops favor sports cards, and Pittsburgh is a little over an hour east.
Columbus has the most shops of any one city, and they are overwhelmingly card-game stores, several of them on the north side along High Street and Bethel Road. Cincinnati is the better stop for sports cards and vintage. Dayton's listings are all sports-card shops, and Springfield, east on I-70, mixes sports, vintage and Pokémon.
Plenty of Ohio shops list vintage cards. Toledo's shops are game stores, and the Ann Arbor shops in Michigan are about an hour north.
Card shows, conventions, and tournaments happening across Ohio.