1883: Thomas W. Sidwell opens Friends' Select School in the back of a Quaker meeting house at 1811 Eye Street.
1910: Sidwell purchases residence at 3901 Wisconsin Avenue. Grounds are used for student recreational activities.
1922: A Lower School building is constructed on the Wisconsin Avenue property.
1936: Thomas Sidwell dies. His school is placed under the care of a Board of Trustees.
1938: The Eye Street campus is sold to Doctors Hospital, and all classes and activities are consolidated on the Wisconsin Avenue campus.
1945: The School sells 3939 Wisconsin Avenue to National Radio Institute to purchase a 10-acre tract across Wisconsin Avenue for athletic use.
1955: The School sells athletic fields across Wisconsin Avenue and purchases a Federal stone structure known as The Highlands. The building currently houses the school administration.
1963: Sidwell Friends purchases 5100 Edgemoor Lane in Bethesda and moves the Lower School to the 5.5-acre property.
1964: The High School (formerly the Sidwell residence) is demolished and a new building is constructed for grades 9-12.
1981: The Robert P. and Arlene R, Kogod Center for the Arts is built.
2006: The new Middle School opens as the first LEED Platinum K-12 school building in the world.
2007: A LEED Gold gym and classroom building open on the Bethesda campus.
2010: A LEED Gold Athletic Center is constructed below the football field .
2011: The Kenworthy Gymnasium, built in 1958, is repurposed as a LEED Platinum Quaker Meeting House with arts classrooms.