Both ends of I-70, plus Springfield
Missouri's listings gather around Kansas City and St. Louis, on opposite sides of the state along I-70. On the Kansas City side they run east into Independence, Blue Springs and Lee's Summit. The Kansas half of the metro, around Overland Park and Olathe, has more.
Around St. Louis, suburbs such as Kirkwood, Olivette and O'Fallon have sports-card shops as well as the city. Springfield, down in the southwest on I-44, has plenty of shops of its own, several of them on Sunshine Street, sports-card stores among them.
Card shows, conventions, and tournaments happening across Missouri.