A causeway has existed at La Fosse since at least the 15th century. It was used to power a mill on the left bank. After 1537, it was fitted with a marinière gate. When the Mayenne was canalized in the 19th century, it was destroyed and rebuilt a few metres upstream. The plans for the new lock dam were studied (and perhaps finally drawn up) by the Ponts et Chaussées engineer Lahougue in 1865. The work, supervised by engineer Legras, was carried out by Brest contractors Buré and Crosnier, who were chosen in the tender held on 12 September 1874. Begun in 1876, they were almost completed in 1877 when they were opened to navigation. However, due to the damage caused by the floods of 1878, 1879 and 1880, they were not finally accepted until 14 March 1882. The lock house was extended at the end of the 20th century.
