Baltimore & Ohio Railroad, Mount Clare Passenger Car Shop, Southwest corner of Pratt & Poppleton Streets, Baltimore, Independent City, MD

Significance: A unique structure, the Mount Clare Passenger Car Shop is undoubtedly the largest circular (actually 22-sided polygonal) industrial building in the world. It is commonly misidentified as a "roundhouse." Erected to build and repair passenger cars, so serving to ca. 1953, it was converted to the B&O Museum's principal building, housing a collection of full-size locomotives, cars, and other large exhibits. The sloping lower roof is supported by radial trusses carried at their outer ends by the brick exterior walls and at their inner by 22 wrought-iron columns that also support the lantern and cupola, and surround the 60-foot turntable. Diameter: 235 feet; height to top of cupola: 123 feet. The exterior walls are built of hard brick and the roof is of slate. The building had room for 22 stalls and is lit by a clear story 100 feet in diameter. The roof rises sharply from the outside walls to the base of the story is brick. In 1974-75, the entire complex was renovated by the Chessie System, including a new slate roof for the car shop.
Unprocessed Field note material exists for this structure: FN-22
Survey number: HAER MD-6