Cos d'Estournel is a relatively new property only being founded as late as the beginning of the 19th century by Louis Gaspard d'Estournel who had inherited a small parcel of land on his fathers death in 1791. He kept buying plots of land enlarging his holdings steadily. At first he had no real plan what to do with his land but one day in 1811 as he was looking towards his neighbour Château Lafite Rothschild, who at that time was the most renowned and expensive of all wines, he started to ask himself if he would not be able to produce great wines as well. Comparing the quality of the soil, the inclination of his land and the nearness to the river he realises for the first time the potential of property.
He was however forced to sell this the same year due to financial problems but was able to buy it back with the help of financial backers ten years later. With this new capital available to him he expanded the size of the property gradually from 12 hectares in 1821 to 57 hectares in 1847.
His second passion was to trade thoroughbred horses in the far east and also to import Arabian horses to France. He thought it may be a good idea to try to sell his wine to his contacts overseas thereby combining his two businesses. Considering that most of his potential customers were muslims it comes as no surprise that this business venture was unsuccesful. So, the unsold casks of wine were returned back to Bordeaux where a discovery was made that would help to increase the reputation of M. Estournels wines.
The wines of Bordeaux in those days were very different to the wines made today. They were, as a rule, harvested earlier and grapes with varied levels of maturity were vinified together without destalking beforehand. This made the wines very tough, acidic and difficult to drink young.
The heat and constant movement of the casks during the journey to the far east and back had accelerated the maturing process of the wines so that they now tasted considerably better than the wines being stored in Bordeaux. This made the wines of Cos so popular that M. Estournel now were shipping his wines to India and back before bottling them adding a labels stating "expédié par moi" and being signed by himself. He invested most of his money into extending the vineyards and to build the exotic cellars and chais that now adorn the labels. This fantasy with its chinese pagodas and triumphal arch were obviously inspired by his love of the far east. It is not clear whether he planned to build a château at one point or the other but soon his money ran out and he was forced to sell Cos a second time in 1852 before dying at the age of 91 the year after.
The new owner was an english banker by the name of Charles Cecil Martyn who showed little interest in winemaking and so hired the owner of Château La Mission Haut Brion, Jérome Chiapella, to administer the property. This further increased the quality and reputation of the wines so that at the time of the Bordeaux Classification of 1855 it fetched prices comparable to those of the more ancient châteaux Rauzan, Pichon and Léoville and was accordingly classified as a Second Cru. Cos was to be sold to a M. Errazu who in turn sold it to the Holstein family who were also the owners of Château Montrose at the time.
In 1917 it was bought by Ferdinand Ginestet, the founder of the famous bordelaise négociant company. This was the first wine property they bought. Château Margaux and Petit Village were to follow.The family properties were divided in 1970 and Cos came into the hands of the Prats family through the marriage to Ferdinand Ginestet's daughter. Her son, Bruno Prats, managed Cos until 1998 when it was sold to the Taillan Group and in 2000 it was sold again, this time to the Société des Domaines Reybier. The management has however remained in the able hands of Bruno Prats son, Jean-Guillaume, since his his fathers retirement in 1998.
Bruno Prats made a number of improvements in the running of the property and its winemaking. It was during his time that Cos progressed from being a good second cru to that of a "Super Second". The grapes were harvested a little later, a better control of the vinification, stricter selection and the more or less elimination of "vin de presse" led to a softer more elegant style of wine.