Buchanan County Infirmary, also known as Buchanan County Poor Farm and Green Acres, is a historic hospital building located in St. Joseph, Missouri, United States. It was built in 1919, and is a two-story, F-shaped Classical Revival-style building with a "fireproof' concrete structure, brick walls, and a cross-hip roof clad with red ceramic tiles. It features a central porch with four full-height concrete Doric order columns that support a projecting, pedimented roof. It is the last surviving structure of the Buchanan County Poor Farm.
It was listed on the National Register of Historic Places in 2009.