The history of the town can be sourced well before the Fifth Century. The town was also at the root of an agricultural faubourg after 1860.
It was founded at the point where the Chaussée Jules César, a Via Romana from Lutèce to Lillebonne, meets the Oise river. The origin of the town’s name stems from Saint Ouen, a counsellor of Dagobert 1st and bishop of Rouen ; and of the Aumône, the neighborhood of the Saint-Lazare malarery(leper house) in the 12th Century.
The village, politically and militarily dependent on Pontoise, lived, in fact, around the royal abbey founded by Blanche of Castille, and the economic and medical activity deployed by the nuns.
In the second half of the 19th Century, the village benefited from rural exodus and with the development of carpentry and engineering factories, its population rose to 3000 inhabitants shortly before World War One.
After World War Two, several apartment blocks were built to meet rising demand for housing, and this movement amplified following the decision to create the new town of Cergy-Pontoise in 1970.
In the mid 1980s, it housed one of the largest zones of activity in Europe.
Saint-Ouen-l’Aumône is gifted with an environment of greenery, founded on the promotion of its natural and historical assets, the county park of the Maubuisson Abbey (13th Century), and the « Coulée Verte » providing a green pedestrian pathway which runs along the rue de Liesse and the Maubuisson ponds.