Although no longer illuminated, the Rock Harbor Light at the southwest entrance to Rock Harbor is the most viewed and visited lighthouse. Completed in 1855, it features a 50-foot white round brick tower with a black lantern. The tower is attached to a keeper's house that now serves as a museum. A Fourth Order Fresnel Lens once sent out a beacon of light for 15 miles across the lake. In 1859, as copper mining declined, the Rock Harbor Light was shut down, but the light was rekindled in 1874 when copper mining resurged. In 1879, it was permanently closed, but remains a popular tour stop for visitors today.
After the signing of the Treaty of LaPointe in 1843 with the Chippewa Nation, Isle Royale was opened to copper exploration and mining. By 1847 more than one dozen mining companies had established sites on the island. Through pressure exerted by the mining companies and the commercial fisherman who used the island as a base of operations, the need for a light to guide and protect ships arriving with supplies was established. The anticipated opening of the Locks at Sault Saint Marie, Michigan, also influenced the decision to place a light on the island to guide ships en route to Thunder Bay, Ontario, Canada.
The first to be built on Isle Royale, Rock Harbor Lighthouse marks the entrance to Rock Harbor at the Middle Islands Passage. In 1847 the location was chosen and preliminary survey work was completed. In 1853 Congress appropriated $5000 for construction. The lighthouse was completed and lit in 1855, utilizing a fixed white light visible for 14 miles.
Because shipping had declined with the decrease in mining activity on the island, the Lighthouse Service chose to extinguish the light in 1859.
A renewed interest in mining in the 1870s stimulated Congress to appropriate $5000 to repair and upgrade the lighthouse. Extensive restoration work was completed in 1874 and the light was reactivated in August of that same year. A woodshed, boat house, and loading dock were also added to the site.
The interest in mining subsided once again, and with the construction in 1875 of the more centrally located Isle Royale Light on Menagerie Island, it was decided to permanently extinguish the light in 1879.
The turn of the century saw the lighthouse being used as a shelter for camping parties. From 1928 through 1939 commercial fisherman Arnold and Milford Johnson resided there. The lighthouse was again abandoned in 1939 when the National Park was established.