During the XVth century, Penmarc'h was a rich harbour, most of their buildings were built at this time. On St. Pierre's Head, a watch tower enabled to warn merchant vessels of presence of pirates. It was also used as light towerfirst, and as semaphore later, which prevents it from demolition, during the construction of the An II lighthouse.

In 1806, birth of semaphore network, the old tower is equipded with mobile wings. Damaged in 1809 during a storm, upper part was made again in 1810, with a reduced top (5 meters less).

In 1831, it became the first lighthouse in Penmarc'h, equiped with a revolving light composed with 4 D'Argand's light and 4 reflectors. It's eclipses succeded every half minute. The light was about 13 meters up to the ground and the range was 4 leagues. In 1835, the old tower became only a semaphore, till 1862, when an other building was errected for it.