Hill was born in New Brunswick, New Jersey. He is a descendant of the Hill Plantation in South Carolina. His mother was a teacher and his father was an Episcopal minister. At the age of two, Hill's family moved to Oakland, California, He attended Scipio Jones High School, where his academic achievements resulted in him securing a scholarship to study at university. He first studied chemistry at Lake Forest College in Illinois. During his time at Lake Forest, Hill became a leader of the Black student community. He spent his final year at the Free University of Berlin. During his time in Germany, the Assassination of Martin Luther King Jr. took place. He eventually returned to the United States and moved to the University of Chicago for his graduate studies, where he completed a Master of Arts in Teaching in chemistry. After completing his teacher training, Hill worked as a chemistry teacher in the Chicago Public School system. Hill became increasingly interested in a career in agriculture, and moved to the University of Arizona to work toward a master's degree in soil chemistry. He joined the University of Illinois at Urbana–Champaign for his doctoral research, where he specialised in agronomy and environmental chemistry.