The Château de Beaufresne dates from the end of the 18th century. It has been modified many times but without losing its essential character. It has a red brick and stone exterior with two towers surmounted by slates and a central pediment. A small stream, the Ru du Mesnil crosses the 10-hectare park and feeds the small lake creating a charming setting.

When Mary Cassatt bought Beaufresne in March 1894, the deed of purchase described it as being located in the commune of Mesnil-Théribus in the canton of Chaumont-en-Vexin (Oise) with its surroundings and dependencies - park, meadow with a spring, water trough, pump, pond, beech wood, mill, waterfall and walled vegetable garden. The artist had previously rented the Château de Bachivillers during the summer months but when the owners wanted to live there themselves, she had to find another seasonal residence. Beaufresne, only a few kilometers away satisfied her requirements for good train connections to Paris and proximity to her friends Camille Pissarro in Eragny-sur-Epte and Claude Monet in Giverny. She was to live there until her death in 1926.

She set about installing all the modern comforts that she was accustomed to from her upper-class American background. Central heating, running water and bathrooms made their entry into Mesnil-Théribus. She had electricity installed and offered, in vain to provide it to the village for street lighting. The park was transformed into a verdant setting with numerous trees and rose bushes.  She restored the mill, still visible today, in which she set up her engraving workshop. It was in this building that she made the prints that made her famous.

Mary Cassatt involved herself in the village affairs of Mesnil-Théribus. For several years she paid the school teacher’s salary and every Christmas she treated all the village children to a tea party.

Mary Cassatt’s 32-year connection to the Château de Beaufresne in Mesnil-Théribus wasn’t the only link with the US. The house used to belong to the family of Admiral François Joseph Paul de Grasse (1722-1778) victor of the naval battle in the Chesapeake Bay in 1781 against the English during the US War of Independence.

In 1961, Ellen Mary Cassatt, Mary Cassatt’s niece inherited Beaufresne and in turn, appropriately, bequeathed the château to the Moulin Vert association, an organization dedicated to family services. Mary Cassatt had a strong commitment to children’s welfare. Representations of women and children were her favourite subjects.