Tillman was born as Dorothy Jean Wright in Montgomery, Alabama to James Wright, a local handyman and Edna Mae Struggs (formerly Wright; d. November 30, 2009). Tillman's parents divorced when she was a child which resulted in her spending her childhood between Montgomery with her father and Pensacola, Florida, where her mother had remarried and relocated to. Tillman joined the Southern Christian Leadership Conference (SCLC) as a trainee and field staff organizer in 1963. Tillman marched with Martin Luther King Jr. and was among the SCLC Field Staff to cross the Edmund Pettus Bridge in Selma, Alabama in the Selma to Montgomery marches on 7 March 1965.