The Causeway, also known as the Tregaron, is a country house estate located in the Cleveland Park neighborhood of Northwest, Washington, D.C.. The estate was designed by Charles A. Platt and constructed in 1912. The original occupants, the Parmelees, lived at the estate from its construction until 1940. From 1940 to 1958 it was occupied by Joseph E. Davies, who had served as the ambassador for the United States to Luxembourg, Belgium, and the Soviet Union. Today the estate serves as a campus for the Washington International School.