TYPES OF HISTORIC AIDS TO NAVIGATION

There are seven basic types of historic aids to navigation that might be considered for nomination to the National Register.

Manned Lighthouses. These structures are lighthouses built with accommodations for keepers and intended to be regularly occupied and operated. Manned lighthouses may be a part of a district including the lighthouse, keeper's quarters, oil houses, cisterns, docks, etc.

Unmanned Lighthouses. These are lights that did not require constant tending. They are generally small individual light towers built to mark a channel or pierhead.

Sound Signals. These are fog signals of all types. Fog signals were generally placed in conjunction with a light and usually form one component of a light station. Sound signals usually are in a separate structure on a station. A few stations were built solely as sound signals, some of which later received lights.

Range Lights. These are pairs of lights, located some distance apart, which are visually aligned by the mariner to delineate a channel or harbor entrance.

Daymarks. These are conspicuous marks, formerly known as beacons, that are used as a visual guide to mariners during daylight hours. While painted rocks and prominent landmarks have served as daymarks, the most common form is the numbered board of distinctive shape and color used to delineate channel boundaries. The shape and markings of the towers of lighthouses served as daymarks. The Cape Hatteras Light tower, for example, was painted with a black and white spiral pattern.

Lightships. These are floating light stations moored offshore or in locales where a lighthouse cannot be built or reach with its light. Lightships are historic vessels and should be evaluated in accordance with National Register Bulletin: Nominating Historic Vessels and Shipwrecks to the National Register of Historic Places. This bulletin should also be consulted when assessing these vessels as aids to navigation.

Buoys. These are moored floating objects of various shapes that serve as daymarks. Some buoys are lighted or support sound signals. Individual buoys are easily portable objects and as such are not generally eligible for National Register listing.

Pieces of equipment from an aid to navigation, detached and displayed apart from their natural setting at a light station, are not considered eligible for listing in the National Register.