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
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.