Even with a light on Pilot Island, mariners still found it difficult to determine the correct turning point for entering Porte des Morts Passage. In 1889, Captain William Nicholson, who regularly sailed between Green Bay and Chicago with the Peshtigo Barge Line, suggested that a pair of range lights be built on Plum Island to indicate the proper bearing for entering the dangerous passage.
The district inspector presented Captain Nicholson’s idea to the Lighthouse Board, who agreed with the recommendation and petitioned Congress in 1890 for $21,000 to finance the station. After repeating its request a few times, the Lighthouse Board finally obtained funding for the project in March 1895. By the time specifications and plans were drawn up for the necessary structures and contracts were put out to bid and awarded, it was too late in the season to commence work that year.
On July 28, 1896, the tender Amaranth anchored off Plum Island, and the first workmen and material were landed. R.I. Hurst supervised a crew of thirty men as they cleared areas for the towers and then cut a swath twenty feet wide and sixteen hundred feet long along the western side of the island to connect the two sites. During August, a landing dock was built on the shore near the site of the rear tower, and a 367-foot-long tramway was run between the dock and the dwelling site.
After these preparatory measures, work commenced on the front tower, rear tower, keeper’s dwelling, fog signal building, boathouse, and oil house. The wooden front tower was originally a two-story structure with a square bottom story and an octagonal second story, similar in design to the front range tower built at Baileys Harbor in 1869. The rear tower, built of iron, consists of a central cylinder containing a circular staircase topped by a watch room and lantern room. The circular watch room has a diameter of eight feet, and the tower measures sixty-five feet from its base to the top of the lantern room’s ventilator ball. Four legs, connected by a network of braces, provide additional support to the tower.
A brick fog signal building was built roughly 1,300 feet northwest of the rear tower, and a dock that extended 210 feet into the lake was built nearby and fitted with pipe to provide water for the duplicate steam-powered fog signals.
Over a half mile of wooden walkways were laid to connect the keepers’ dwelling with the various outbuildings. The station was declared complete on December 4, 1896, and on March 17, 1897, Martin Knudsen left his position as keeper at Pilot Island to assume command of the new Plum Island Range Lights. His first assistant was Hans J. Hanson, who was formerly the second assistant at Pilot Island, and Knudsen was told to hire a laborer of his choice as second assistant. Knudsen selected George Cornell, a friend and fellow Washington Islander, who proved well suited for the work and was appointed keeper of Racine Reef Lighthouse in 1906, after having served as a first and second assistant at Plum Island.
Following more than a month of preparation, the keepers finally exhibited the range lights on Plum Island for the first time on May 1, 1897. Fixed, red lights were shown from both towers, with the front light using a sixth-order lens, and the rear light employing a fourth-order Fresnel lens manufactured in France by Sautter, Lemonnier, & Co. The front light was visible in a small arc over the range, which had a bearing of 330°, while the rear light shone over an arc of 231° so it could be seen by mariners entering Death’s Door from the west. The rear tower thus served as both a range light and a lighthouse.
The fog signal did not have to be used until May 9, 1897, when its distinct signal of a three-second blast followed by seventeen seconds of silence first boomed out over Death’s Door.
Keeper Knudsen was transferred to Racine Pierhead Lighthouse in August 1899, and Hans J. Hanson was promoted to head keeper at Plum Island. Keeper Hanson exchanged assignments with Charles E. Young, keeper of Menominee Pierhead Light, in 1905. Menominee and Plum Island had another interesting connection, as it was the Ann Arbor Railroad car ferries, sailing across Lake Michigan between Menominee and Frankfort, that dictated the operational season at Plum Island. The station was typically closed from early January through the first part of April.
Joseph Boshka replaced Young as head keeper in 1907. Four years later, Joseph Boshka was transferred to Holland Harbor, Michigan, and his brother, Charles Boshka, who had been serving as keeper at Pottawatomie Lighthouse, was appointed head keeper at Plum Island in his stead. Charles Boshka retired in 1925, after serving at Plum Island for nearly fourteen years, the longest tenure of any head keeper at the station.
In 1931, a new compressed-air fog signal replaced the old steam fog signal. The existing fog signal building was modified to accommodate oil engines, air compressors, and a tyfon fog signal, along with generators for supplying electricity to the range lights. A marker radiobeacon was placed in operation on Plum Island in 1941. Two years later the radiobeacon was increased to a class “C” beacon.
After World War II, the Coast Guard , which had absorbed the Lighthouse Service in 1939, consolidated its operations on Plum Island. The range lights were automated, the keepers’ dwelling boarded up, and a crew living at the life saving station on the other side of the island was given charge of the lights and fog signal. A wooden watch room was added to the brick fog signal building during this period.
The original front range tower was replaced in 1964 by a steel skeletal tower. Unnecessary and falling into disrepair, the station’s barn, oil house, privy, boathouse, and docks were demolished. The fog signal was discontinued in 1975, leaving only the range lights to serve marines. The Coast Guard abandoned the life saving station in 1991, moving its operations to Washington Island. After being used as a base for helping mariners for more than a century, Plum Island was left uninhabited.
In October 2007, Green Bay National Wildlife Refuge was enlarged to include Plum and Pilot Islands, and control over the island was transferred from the Coast Guard to the U.S. Fish and Wildlife Service. Under the leadership of Tim Sweet, The Friends of Plum and Pilot Island was formed in 2007 to work with the USFWS in preserving the historic structures on Plum Island that are now listed on the National Register of Historic Places. In 2010, the volunteer group repainted the boathouse, which it is hoped will one day serve as the visitors’ center for the Green Bay National Wildlife Refuge.