Montlhéry lay on the strategically important road from Paris to
Orléans. Under the
Merovingians, it was owned by the church in
Reims and in 768 it was given to the abbey of St. Denis in Paris. It was the site of a number of battles between the lords of Montlhéry and the early
Capetian monarchy. The Montlhéry noble house was related to the
Montmorency family; Thibaud, the founder of the Montlhéry dynasty, was the brother of Bouchard II, the progenitor of the Montmorency house. Thibaud ruled from 970 to 1031 and was succeeded by his son
Guy I, who ruled until 1095. Guy I's children married into other local noble families: his daughter Melisende married Hugh,
count of Rethel, and another daughter Elizabeth married Joscelin of Courtenay. Through these marriages and subsequent Montlhéry participation on the
First Crusade, Guy I was the ancestor of the ruling dynasties of the crusader
Kingdom of Jerusalem and the
County of Edessa. Another daughter, Alice, married into the
Le Puiset family, and a son, Guy, became count of
Rochefort. Guy I was succeeded by Milo I, followed by Milo's sons Guy II and Milo II. In 1118, after many disputes with the rebellious lords,
Louis VI of France ordered the castle to be dismantled and turned the town into a royal residence. Louis VI had himself been married to a granddaughter of Guy I, Lucienne of Rochefort, from 1104 to 1107. After being absorbed into the royal domain, Montlhéry became part of the territory governed by the viscount of Paris. In the early 13th century, the French king
Philip II (Augustus) completely rebuilt the castle in the contemporary style, at a new site high above the town. During the
Hundred Years' War, the town and the castle frequently passed between
English and French forces. On 16 July 1465,
Charles the Bold defeated
Louis XI of France at the
Battle of Montlhéry. The town was left in ruins by the
Wars of Religion, but it was rebuilt in 1591 under
Henry IV. In the 19th century, the tower was used for scientific experiments. In 1822,
François Arago calculated the
speed of sound there; a
cannonball shot at the tower was observed from the Observatory of
Villejuif. In 1823,
Claude Chappe installed a relay for the Paris-
Bayonne telegraph line. On 5 June 1874,
Alfred Cornu tried to calculate the
speed of light between the tower and the Observatory in Paris. During the
Franco-Prussian War, the town was occupied and pillaged by the
Prussians. It was occupied again by
Germany in 1940 during the
Second World War. Today Montlhéry is twinned with
Stetten am kalten Markt,
Germany. ==Population==