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Maryland's National Register Properties

Tour: Lighthouses (6 of 8)



Photo credit: Heather R. Davidson, 1993
Seven-Foot Knoll Lighthouse
Inventory No.: B-4222
Date Listed: 8/22/1989
Location: Pier 5, Inner Harbor, Baltimore, Baltimore City
Category: Structure
Period/Date of Construction: 1923-1954
Architect/Builder: Architects: Owens and Sisco

Description: The Seven-Foot Knoll Lighthouse is a wrought iron house on a base of cast iron columns, braced by wrought iron tension members. The original house was described as being square, of cast iron panels, but the present one is round, of rolled iron plates, drilled and riveted together. The present house has two stories, plus a lantern which houses the light. The first floor is 51' in diameter, including a 5' exterior platform. The second story is 15' in diameter, and the light chamber itself is 6' across. The house is supported on nine cast iron screwpiles, one in the center and eight arranged radially 20' from it. The radial piles are connected around the circumference by 4" square bar girders. The girders are connected at the piles by cast caps with pin connections for both the girders and the wrought iron tension members that provide cross bracing. The caps also have bolt-through flanges to support the vertical columns which support the house. The columns have similar caps with connections for the girders that support the house. The girders around the circumference are an unusual fish-belly design, characteristic of early cast girders, rather than rolled sections. Another set of girders run radially to the center hub to support the iron plates of the floor system. A small wooden platform is suspended from them on wrought iron hangers. The present house is made of rolled iron plate much in the manner of rivited iron-hull construction. Three horizontal bands of 3' x 6' plates form the exterior wall with a narrow soffit band forming the connection with the plates which form the shallow cone of the roof. As in ship construction, the pattern of plates, including the cuts for doors and windows, was carefully laid out in advance and the cuts made in a shop with large fabricating machinery. Since the strength demands did not approach those of a ship at sea, there was no need to overlap the plates. Instead, plates are butted and riveted to a 6" strip on the exterior surface. The roof plates terminate in a gutter which forms the catchment system for the lighthouse water supply held in large interior water tanks. The second story of the house is much smaller than that on the original, being only 15' in diameter. It housed the oil tanks and a self-feeding mechanism for the light above. It is pierced by two openings with 2/2 double-hung sash. Significance: Built in 1856 at the outer entrance to Baltimore's harbor near Riviera Beach in Anne Arundel County, the Seven-Foot Knoll Lighthouse was the second screwpile structure built by the U.S. Lighthouse Service. The present structure contains some elements of the original cast iron structure and the house dates from the late 19th century. The light is historically linked to the development of the Port of Baltimore and sits beside one of the busiest shipping lanes on the East Coast. Technologically, the screwpile form illustrates Amercians' ability to produce large cast iron foundry castings, the same development that produced cast iron architecture. In the period 1835-1860, Baltimore was a leading national center of this new metalworking technology and of new marine engineering techniques. Seven-Foot Knoll is arguably the most significant of the remaining screwpile structures. It is now located on Pier V in Baltimore's Inner Harbor.
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