The annex behind the courthouse features collections of firearms, canes, Native American artifacts, a gambling parlor, horse tack, George Catlin art, toys (Buddy L, Marklin, ships, vehicles, automatons and more), trains and accessories including extensive Lionel and Marklin, tools, blacksmith tools, locks and more.

The main level of the museum’s annex, featuring the King Collections, opened to the public in March 2025. The full annex opened in September 2025.