King William High School is located in the Central Garage area of King William County near the intersection of Routes 30 and 360. The school has a rich history dating back to the early twentieth century, when it was first established as Central High School.

In 1924, the Racial Integrity Act was passed by the Virginia General Assembly, which began a long period of legal racial separations that included African Americans, indigenous Americans, and others. The Upper Mattaponi Indian Tribe (UMIT) already had established the Sharon Indian School in 1919, a one-room building which served as an educational center for the Upper Mattaponi children for more than 50 years. The county's African American children also attended segregated schools, including the King William Academy which was founded in 1903 by the Rev. Dr. Samuel B. Holmes. The Academy later became the King William Training School in 1922, built at its current location on Route 30 near the intersection with Walkerton Road, with financial support from the Julius Rosenwald Fund to provide both academic and vocational training to African American children of high school age.

Prior to the establishment of the Sharon Indian School and the three Rosenwald schools (Mt. Olive, Rucker, and King William [Academy] Training School), there were no public schools for African American or indigenous American children in the county.

In 1924, six small county public schools offered two or more years of high school for Caucasian students: Acquinton, Beulahville, Mangohick, Venter, Sweet Hall, and West Point. Through consolidation, two high schools eventually remained, West Point and Central High School, which initially was located at Sharon Church until the original King William High School building was constructed in 1925.

The last class of the King William Training School was in 1950 and shortly thereafter, a new high school for African American children was constructed across the street: Hamilton-Holmes High School.

Long after the landmark 1954 Brown v. Board of Education SCOTUS decision, and several years after the 1967 Loving v. Virginia SCOTUS case that overturned the Racial Integrity Act, schools in the county finally were integrated. The first UMIT citizen entered King William High School in 1963, and the last class from Sharon Indian School graduated in 1965.

By 1970, King William High School was the county's fully-integrated high school.