Old Castle Hall was the first building of Baker University in Baldwin City, Kansas. It was built in 1857–58 to house the university on its first two floors, with the Palmyra Masonic Lodge occupying the third floor. It was used for classes until 1871, when other buildings were constructed for the purpose, and later used as a mill, a dormitory and for storage. The third floor was rebuilt during its service as a mill to address structural problems.