Early life and career
De La Beckwith was born in Colusa, California, the son of Susan Southworth Yerger and Byron De La Beckwith Sr., who was the town's postmaster. His father died of pneumonia when he was five years old. One year later, De La Beckwith and his mother settled in Greenwood, Mississippi, to be near family. His mother died of lung cancer when he was 12 years old, leaving him orphaned. He was raised by his maternal uncle William Greene Yerger and his wife.
In January 1942, De La Beckwith enlisted in the United States Marine Corps, serving as a machine gunner in the Pacific theater of World War II. He fought in the Battle of Guadalcanal and was shot in the waist during the Battle of Tarawa. He was honorably discharged in August 1945.
After serving in the Marine Corps, De La Beckwith moved to Providence, Rhode Island, where he married Mary Louise Williams. The couple relocated to Mississippi, where they settled in his hometown of Greenwood. They had a son together, Delay De La Beckwith. De La Beckwith and Williams divorced. He later married Thelma Lindsay Neff.
De La Beckwith worked as a salesman for most of his life, selling tobacco, fertilizer, wood stoves, and other goods. In 1954, following the United States Supreme Court ruling in Brown v. Board of Education that segregated public schools were unconstitutional, he became a member of a newly formed organization, White Citizens' Council. The group was formed in Mississippi that year in order to resist integration and maintain the exclusion of blacks from the state's political system.