Thomas Watson Sidwell opened Friends’ Select School (as Sidwell Friends was then known) in 1883 as an initiative in co-ed, urban day-school education. Sidwell, then 24 years old, had been a teacher at Baltimore Friends School, headed at the time by Eli Lamb, a leading Quaker educator. Lamb opened the way for Sidwell to begin a school in Washington by sponsoring authorization of the venture within the Baltimore Yearly Meeting. While the Alexandria Monthly and Baltimore Yearly Meetings offered some nominal assistance, this was, from the beginning, a proprietary operation.

Sidwell’s school began with eighteen students in rooms that were part of the Friends Meeting House located in the 1800 block of I Street, four blocks from the White House. Just twenty years after Friends’ Select opened its doors, Sidwell’s school—with fully elaborated primary, intermediate and high school departments—enrolled nearly 200 students. Several buildings, including one of the first gymnasiums to be built in Washington, were eventually added to the I Street campus.

During the 1885-86 school year, a recent Vassar graduate joined the growing faculty. Frances Haldeman was hired to teach Greek, English and history. In 1887, Thomas Sidwell married Haldeman and also made her Co-Principal. The Sidwells would continue to share the leadership of the School for the rest of their lives.

In 1906 the first of a series of changes to the name of the institution that Thomas Sidwell had now presided over for twenty-three years began. The name “Friends School,” or simply “Friends,” came into currency at that time over “Friends’ Select.” Among the later variations on those names was “Sidwells’ Friends School,” the plural possessive emphasizing the Co-Principals’ joint interests.

The Sidwells soon embarked upon a plan that would allow their institution to begin to make the transition from a rural to a suburban school. In 1911, they purchased a Dutch Colonial house and grounds at 3901 Wisconsin Avenue from the Washington School for Boys. While the property served at first as the Sidwells’ private residence, it would soon be used by I Street students for athletic and recreational activities.

By the mid-1920s, the Wisconsin Avenue campus was no longer used exclusively for recreation and sports. A new building called the “Suburban School” (housing primary grades) was constructed from timbers allegedly taken from Woodrow Wilson’s inaugural viewing stand. Other portions of the Friends School academic program would soon be relocated from I Street to Wisconsin Avenue.

With the advent of the Jazz Age, the School’s program and learning community had developed several distinctive aspects, including an emphasis on a high-quality college-preparatory academic program and college placement; a commitment to co-education that included active encouragement of girls to study science, mathematics and industrial arts as well as to participate in sports and physical education; cultivation of enrollment from Washington, DC’s political and diplomatic communities (thus creating a geographically and ethnically diverse student body); a talented and dedicated faculty, including a substantial number of college-educated women; and an ongoing identification with the Society of Friends that was not formalized by any tie with a monthly or yearly meeting.

The death of Frances Haldeman-Sidwell in 1934 convinced Thomas Sidwell of the need to take certain actions to secure the future of the School. In prelude to the 1934-35 school year, “The Sidwell Friends School” was incorporated as a non-profit institution under a Board of Trustees. The Board’s by-laws stipulated that a majority of its members must belong to the Religious Society of Friends. In addition, Thomas Sidwell, in his will, identified a group of twenty-four veteran teachers, two grounds managers, and eleven servants among whom the value of the School’s property was to be divided if the School should fail. Despite the tough times of the Great Depression, the School survived.

When Sidwell died in 1936, the institution he had founded fifty-three years earlier was ready to be guided by the trustees and Headmaster Albert E. Rogers. Within two years, the I Street campus was sold to Doctors Hospital and all operations were consolidated on Wisconsin Avenue.

Sidwell Friends benefited greatly from the District of Columbia’s dynamic growth during World War II. At that time, the School pioneered the development of a fifth-through-eighth-grade Middle School that was among the first in the country. Sidwell Friends School’s first building campaign led to the construction of a separate Middle School building in 1950. In 1955, the School sold playing fields on the west side of Wisconsin Avenue (where McLean Gardens, Fannie Mae, and 4000 Wisconsin now stand) to finance the purchase of an adjacent historic structure known as the Highlands. This building, constructed between 1817 and 1827, was soon renamed Zartman House in honor of Helen Zartman, a key aide to Thomas Sidwell.

Sidwell Friends continued to grow in the 1960s. The School purchased the Longfellow School for Boys in Bethesda, Maryland, and moved its primary grades to that location on Edgemoor Lane in time for the 1963-64 school year. The purchase of the Edgemoor Lane property for a Lower School was directly connected to the demolition of the Sidwells’s Dutch Colonial, which was then being used for high school classes. In order to make room for the construction of a new, modern high school facility, the old Suburban School was razed and its primary age students moved to Bethesda. The Upper School building opened during the 1964-65 academic year.