Missouri 64B is one of only two Missouri highways with a letter suffix (the other one is Missouri 64A). It's a two-mile spur into the Pomme de Terre State Park on the south side of Pomme de Terre Lake in Hickory County.
The west end of the highway (left) ends in the park. The east end of the highway (right) hooks up with Missouri 64 between Pittsburg and Nemo.
More views of each end of the highway are here.