The Four channel runs along the end of the Léon and avoids the bypass west of the archipelago of Molène and Ouessant. Shortcut useful but dangerous, it was for a long time very imperfectly indicated. In the early 1860s, the Nautical Commission approved the construction of a lighthouse at each end of the channel and the first recognition took place in June 1862.
The “roche du Four”, a granite block a block of granite 25 meters in diameter and a height of 11.50 meters with at the top, is the most suitable for the establishment of the work. A first project of a square tower, directly inspired by another lighthouse, at the time under construction, is proposed, but, at the end, it was decided for a round tower identical to that designed to the lighthouse Pierres-Noires, south of the channel.
The work begins the same year but is much more difficult than expected, because of the very powerful currents that converge on the rock and make the landing dangerous as soon as the sea becomes a bit rough.
Despite the proximity of the port of Argenton, only 1.6 nautical miles away, the works lasts eleven years, barely slowed down by the War of 1870. Several accidents occur during the work, the most dramatic in April 1873 when three men die drowned after the flipping of their service canoe. The tragedy will be repeated one hundred years later with the drowning of two guards in December 1978. The construction of the lighthouse ends in 1873 and the lighthouse is lit in the night of March 14 to 15, 1874. It is built of granite stone and rests on an irregular base of concrete and stone laid out as a landing stage. The tower is 28 m high and the interior includes an entrance and five floors connected by a spiral staircase on the back of the tower: reserve food and freshwater cistern, kitchen, bedroom, engine room and finally room of honor. A cast iron staircase connects it to the lantern chamber which houses the mercury cell (1913) on which rests the rotating optics set up the same year during the transition to combustion with petroleum vapors, and still operational. The current white light delivers 5 bursts grouped every 15 seconds, with a range of 24.5 miles.
The lighthouse will forever remember some events, in its history:
On February 13th, 1913 the lighthousekeeper died, due the emanation of oil.
The lighthouse is automated since October 6, 1993, and It is no longer guarded.
On December 9, 1978 the sinking of the supply boat Ouessantine, swept by the waves. The two sailors managed to regain the lookout but the two guards died in the waves.
Since April 20, 2017 the lighthouse is classified as historical monuments by order of the Ministry of Culture and Communication.