Combining keeper's quarters with the light itself, this two-story octagonal structure is the only one of the first twelve lighthouses in Alaska that has not been substantially altered. Between 1902 and 1906 the Board of Lighthouses constructed a dozen lighthouses in Alaska, four of them in Lynn Canal, in response to the unprecedented traffic to the goldfields. Eldred Rock, the last of those twelve, was completed in 1906.

The first Alaska lighthouse to be constructed of concrete, the building has a concrete first floor and wood-framed second floor. An irregular octagon in plan, 52 feet in diameter, the structure has a cupola rising from the peak of its pyramidal roof, to a total height of 56 feet. The fourth-order light, displayed 91 feet above high water, was visible for about 15 miles. In 1973, Eldred Rock was unmanned and downgraded to a minor light.