Johnson was born in Ashley, Pennsylvania on November 10, 1924. His parents were Russell Kennedy Johnson (1901–1932) and Minnie Wenonah Smink-Johnson (1902–1976). Johnson was the second-oldest of six children. His siblings were brothers Kenneth (1925–2012), David (1926–1976), and Paul Wesley (1932–1933), and sisters Lorraine Johnson-Crosby (1928-2015) and Marian L. Johnson-Reeves (1923–2010). Their father died of pneumonia in December 1932; the youngest of the siblings (Paul Wesley Johnson), died not long after. Minnie Johnson later remarried to Thomas S. Lewis. As a teenager, Johnson attended Girard College, a private boarding school for fatherless boys, located in Philadelphia.