Mark Kirwan, an Irishman, acquired the property from Englishman John Collingwood in 1760 after marrying Collingwood's daughter. He built the château and branded the label with his name to make it easier for merchants to identify and sell. Thomas Jefferson, a lover of Bordeaux, wrote about Château Kirwan (Quirouen, at the time), and listed it as a second classified growth. This was, however, before 1855, when it was officially classified as a third growth. The Kirwans sold the winery in 1827. Château Kirwan is situated on 40 hectares (100 acres) the Cantenac Plateau on the Garonne River. Studying the soil composition, Cabernet Sauvignon is the dominate variety grown here, thriving on gravelly soils, while Merlot enjoys more clay-based soils on another part of the property. Some Cabernet Franc and Petit Verdot are grown as well. Château Kirwan believes in minimally invasive techniques in the wine cellar, calling winemakers "wine helpers" instead. The wine is aged for 20 months in 40 percent new French oak, allowing the quality of the fruit and soil structure to shine. Often described as elegant, silky, and firmly structured, it is considered a classic example of Margaux. In addition to the grand vin, they also make a second wine called Les Charmes de Kirwan.