Located at the Old Castle Complex is the Palmyra Post Office and Blood's Grocery which opened in 1857. Originally located north of the highway on the Santa Fe Trail, it served travelers on the trail and the pioneer community of Palmyra, the original townsite later to become Baldwin City.
Many of the original trappings of the post office are on display. Notice the rocks that were put inside the walls as protection against stray bullets during "Bleeding Kansas" border raids.