John King Cochran was born on August 5, 1832, in Charlottesville, Virginia, to John and Margaret Cochran. His father was a farmer who owned $45,000 of real estate and $60,000 of personal property by 1860. He grew up and attended school in Charlottesville, and he attended Jefferson Medical College. He married Elizabeth Brooke on April 17, 1856, and the couple apparently had no children. By 1860, he was working as a doctor in Charlottesville.
He sided with the Confederacy during the Civil War, and he served as an assistant surgeon. He returned to Charlottesville after the war and resumed his work as a doctor. He eventually moved to Seven Mile Ford, Virginia, and he died there on November 28, 1903.