Founded by members of the Reformed Presbyterian Church,[2] Westminster Christian Academy opened in 1976 in rented classrooms at Missouri Baptist University, with 72 students.

[3][4] The Ladue Road campus, which originally had a capacity of 600, was renovated and expanded in the early 1990s to accommodate 900 students, and enrollment subsequently grew.

In 2003, Westminster purchased the 40-acre campus of West County Vocational Technical School in Town and Country, intending to use it to accommodate future growth.

An anonymous gift enabled it to purchase the adjacent 30 acres, known as "Centreat", from Central Presbyterian Church.

[6] The following have served as head of school: Nolan Vander Ark (1976–77); Evelyn Downs (1977–81); Arlen Dykstra (1981–84); Larry Birchler (acting headmaster 1984–85);[citation needed] Jim Marsh (1985–2013);[6] Tom Stoner (2013–2016); Barrett Mosbacker (2017–present).

[9] During the 2018–19 school year, 15 students were selected to participate in the St. Louis metro district honors choir and orchestra.