Johnson grew up in Tampa, Florida. She was an only child, and her household consisted of her, her mother, and her mother's husband. They lived in the parsonage of their conservative Pentecostal church.Beginning at age 8, Johnson was repeatedly raped by the bishop and deacon of her church. Johnson was also raped by her mother's husband. She became pregnant as a result of rape at age 10. The pregnancy was not recognized until she was 7 months along in gestation. Johnson's mother did not support or believe her statements that she was raped, and did not accompany her to the hospital when it was time to deliver the baby. Johnson's mother arranged for her to marry the deacon who had raped her, Alfonsa Tolbert, so that he could avoid criminal charges.
At the time, 16 and 17 year old minors could get married with parental permission in Florida, and children of any age could be married with the permission of a county judge if a pregnancy was involved. While the first judge refused to license the marriage of a child so young—though it was legal—a second judge agreed to grant the license and Johnson was married to Tolbert on March 29, 1971, at age 11. Johnson had six children by the time she was 17-years-old, and had to drop out of school after ninth grade to raise them. At age 17, she sought help from Legal Aid Society, which gave her $75 to pay for an attorney for her divorce.