Knox was born on January 5, 1904, in
New Bedford, Massachusetts, to William Jacob Knox Sr., a US postal worker, and Estella Briggs. William Sr. had a
slave heritage as his grandfather, Elijah Knox, was an enslaved carpenter in
Edenton,
North Carolina. Elijah's eldest child was
Harriet Jacobs, the author of
Incidents in the Life of a Slave Girl. According to family tradition, William Jacob Sr. was given his middle name "in honor of his aunt Harriet and his uncle
John S." The Knox family had a strong "tradition of upward mobility through education". During his time at Harvard, William faced persecution and fought racist discrimination. He was accepted into Harvard University's undergraduate program in 1921. He was told to report to the freshman housing once he arrived for the semester. Upon arriving, Knox was immediately ousted for being black and was forced to give up his room in the
whites-only dormitories. This confrontation with the housing at Harvard and many other instances such as realtors only offering an abandoned brothel may have influenced Knox heavily, as he would join the
National Association for the Advancement of Colored People (NAACP) in Rochester, New York, after his work in the Manhattan Project. William Knox confronted discrimination head-on by receiving further education. In 1929, Knox began to teach at
Howard University, a private university in Washington, D.C. While instructing at Howard, Knox was introduced to his wife, Edna Lenora Jordan. Knox and Jordan were legally wed on September 1, 1931. Together they had one child, Sandra Knox. == Early professional work ==