Between the 13th and 16th century the statue, known as Notre-Dame de la Mer ("Our Lady of the Sea"), became a popular object of pilgrimage, bringing prosperity to the town.

In 1567, on the creation of the Diocese of Boulogne, the church was elevated to be its cathedral, and flourished until the French Revolution, when the Civil Constitution of the Clergy of 1790 brought it under government control.

A local priest and self-taught architect, Benoît Haffreingue, vowed to rebuild the destroyed cathedral to restore the honour of Our Lady of the Sea and return the episcopal seat to the city.

After a vigorous campaign he was able to gain the support of many, including Victor Hugo and François-René de Chateaubriand, and soon had considerable public opinion behind him.

During their reconstruction the whole building was reinforced with concrete, which without doubt allowed it to survive the bombing received by the city during World War II.

When Haffreingue began work on the new church in 1827, the workmen discovered a crypt that had lain unknown for centuries, having probably been filled in during the 1544 siege of Boulogne by Henry VIII of England.

The crypt includes a chapel in which the body of José de San Martín, the South American liberator, was buried between his death in 1850 and its return to Buenos Aires in 1861.