The local tradition attributes it to Theuderic IV, the penultimate Merovingian king, who was imprisoned by Charles Martel, without a reliable source.

In the late years of the western Roman empire, a small town called Otmus was settled on a site where the Soissons-Troyes road crossed the Marne river.

In 946, the castle of Château-Thierry was the home of Herbert le-Vieux, Count of Omois of the House of Vermandois and Soissons.

[3] Formerly the capital of the district of Brie Pouilleuse, Château-Thierry was captured by the English in 1421; by Charles V, Holy Roman Emperor, in 1544; and by the duke of Mayenne in 1591.

[5] In 1918, a mounting for the Paris Gun was found near the castle, though the cannon itself had apparently been moved prior to the emplacement's discovery.