Mary Institute and St. Louis Country Day School

William Greenleaf Eliot, founder and chancellor of Washington University in St. Louis, established predecessor institutions to MICDS in the 1850s as part of the university. A boys' school, Smith Academy, was founded in 1854, and was later attended by Eliot's grandson, the future poet T. S. Eliot.

A sister school for girls, Mary Institute, was founded in 1859 and was named for Eliot's late daughter Mary Rhodes Eliot, who had died at 17. In its early years, Mary Institute moved twice within the city of St. Louis; its third building, at the corner of Lake and Waterman, is now New City School.

Smith Academy closed in June 1917, in part due to the proliferation of private elementary schools and public secondary schools in the area. Three months later, St. Louis Country Day School opened in northwestern St. Louis County. Inspired by the Country Day School movement nationally, it was not related to Smith, although a number of former Smith students enrolled that first year. St. Louis Country Day School's campus was in a bucolic setting reached by electric streetcar, far removed from the noise and grit of the city.

Mary Institute moved to its Ladue campus in 1931 and became independent of Washington University in 1949. By the 1950s, the tranquility of the Country Day campus was disrupted by the growth of the adjacent Lambert–Saint Louis International Airport. St. Louis Country Day School moved to a new campus next to Mary Institute in Ladue in 1958, and eventually sold its old campus to the airport.[3]

Eliot's grandson, Nobel laureate T. S. Eliot, who attended Mary Institute's kindergarten and Smith Academy, spoke at Mary Institute's centennial in 1959. Although various connections, including theatrical cooperation, had existed between Mary Institute and St. Louis Country Day School for years, academic coordination between Mary Institute and Country Day began during the 1970s and culminated in the 1992 merger of the schools.

St. Louis Country Day headmaster John Johnson, who coordinated the merger, became head of the combined schools. The school observed its sesquicentennial during a year-long celebration that ran from May 11, 2009 through May 11, 2010.

MICDS opened a STEM building on the Upper School campus in 2013 that contained classrooms, an auditorium, a hearth room, and a student commons. The space also contains conference rooms, a faculty office space and work center, a robotics garage, and a science lab for independent research. The building is certified as LEED Platinum.

MICDS teams have won 32 state championships and 41 district championships.[4]

The school has one of the only high school cycling teams in St. Louis, which has come in second place in several local races. They competed in the Tour De St. Louis in 2009; two MICDS riders finished with the peloton.[5]

MICDS has a standing athletic rivalry with the nearby John Burroughs School. MICDS observes its Homecoming on the weekend when all of the teams play Burroughs; there is a traditional bonfire and pep rally to inspire team spirit. MICDS also has a cross-state rivalry with The Pembroke Hill School in Kansas City.

Pro Football Hall of Fame inductee Marv Levy began his coaching career here in 1951, staying for two years.

The women's varsity field hockey team won the Midwest Championships in 2013, 2014 and 2015.

Men's water polo won third place in state in 2014.

The Men's lacrosse team has won eight state championships, including six straight championships since 2014 under head coach Andy Kay.[6]

• Mary Institute and St. Louis Country Day School