St-Omer

Town in Pas-de-Calais département, northern France, 42 km/26 mi southeast of Calais on the River Aa; population (1990) 15,300. It is the centre of an active market-gardening region, and there are foodstuff, textile, glass, and paper manufactures. In World War I it was the site of British general headquarters from October 1914 to March 1916.

Features The huge basilica of Notre-Dame, formerly a cathedral, was built between the 13th and 15th centuries and has a 16th-century astronomical clock. The town also has two museums and a ruined abbey. The surrounding marshland provides leisure-boating facilities and transport for the agricultural market-garden produce, especially cauliflowers.

History On 9 May 1469, by the Treaty of St Omer, Sigismund, Count of Tyrol, mortgaged to Charles the Bold of Burgundy Upper Alsace and other land already pledged to the Swiss. The executioner who beheaded Anne Boleyn, second wife of Henry VIII of England, in 1536 came from St-Omer. The town was taken by Louis XIV in 1677 during the Third Dutch War. The mathematician Joseph Liouville was born here in 1809.