Fresnel lenses for lighthouses are come in 6 primary sizes (called orders) with first order lenses only used on ocean lighthouses. Only a few 2nd Order lenses were used on the Great Lakes, with the 4th Order being the most commonly used.
The Kewaunee Pierhead Lighthouse Fresnel Lens is a fifth-order lens. That means it has a height of 21.3 inches, a focal length of approximately 7.5″, and weighs approximately 275 lbs. Its useful visual distance is about 15 miles which is average for a lens of this size. Such a lens would have cost about $950 to make in 1900 which would equate to over $26,000 in today’s currency. (according to the US Lighthouse Society)
The lens was manufactured by Barbier and Fenestre in Paris, France, however we’re unsure exactly when. The lens is designed as a fixed lens for 270 degrees of its frame, with the quarter of the frame facing shore as a reflector panel. This reflector panel also doubles as a door, providing the access to the lamp, or in modern time, the electric bulb changer.
Kewaunee Lighthouse Lens Today
The Fresnel lens was replaced with an LED light by the USCG in June of 2019. The old lens is now housed in a display case as part of the lighthouse preservation project, and is located at the Kewaunee County Historical Society.
The lens is slowly lowered out of the tower 
Kurt Fosburg cleans the lens prior to putting it on display (Robin Nelson)
