The seaside resort of Les Rosaires was created in the early 20th century by the Parisian architect Paul Marteroy and the automobile manufacturer Lucien Rosengart. He built the villa Ker Avel, current sailing school of Rosaries, and the Hotel Rosaria, now restaurant La Balnéa). The great road leading from Saint-Laurent to Rosaires was built and classified in 1912. The station developed after the creation of the union of initiative in 1926 and experienced a real boom during the second half of the 20th century. The first dike of 280 meters in length was built in 1937. It has been redesigned and extended several times during the 20th century. Newer habitat is installed along the main road to the beach and on the cliff heights. At the end of the promenade, we can notice a blockhouse and a tobrouck, dating from the Second World War. The old bath cabins have been replaced by a row of terrace cabins.