The last remaining signal tower in the United States, the Portland Observatory is a battened octagonal tower rising roughly eighty-four feet in height. Built in 1807 by Captain Lemuel Moody, the tower served merchants on Portlands wharves by announcing the approach of ships in the outer harbor. Its shape is described in John K. Moultons Portland Observatory: The Building, The Builder , The Maritime Scene as thus:
Its diameter at the base is thirty-two feet and it tapers to fifteen feet at its top. This is surmounted by an open three-foot deck and an enclosed lantern, or observation deck, eight feet across. A quasi-hemispherical dome caps the structure. From a distance the top appears to be a hemisphere, but closer examination reveals its true shape. Eight curved triangles, Riemannian in nature rather than Euclidean, make up the cap. Each triangle has its base on a beam of the enclosure of the lantern, then curves up and into a common apex
.The Brown Tower is anchored at the base by large fourteen inch square cross beams covered by 122 tons of rubble stone.
Work includes an analysis of the existing conditions of the tower; preparation of HABS level measured drawings, preparation of construction documents for restoration, and construction administration services during the dismantling of the tower, preservation of timber framing members and reconstruction of the tower. In addition, a new entrance is being designed to make the Observatory universally accessible as required by the ADA. Work on this project began August 1998.
Photograph by Brian Van de Brink