Cabaniss was the first of four children born to George Augustus and Juliet McKay Cabaniss of Monroe County, Georgia. After completing grammar school in Forsyth he earned bachelor's and master's degrees at Mercer University in Macon, Georgia. He then completed law school at the University of Virginia and was admitted to the Alabama State Bar from Union Springs in Bullock County. He married the former Martha Frazer Jelks, the sister of newspaper editor and future governor William Jelks, on December 13, 1882. The couple had five sons: Robert, Edward Jr, Jelks, Elbridge and William.
In 1886 he was elected to the Alabama State Senate, but resigned in 1887 in order to relocate his law practice to the fast-growing city of Birmingham. He moved his family to a home at 2251 Highland Avenue (now the site of the Highland Towers apartment building), and became a partner in the firm of Cabaniss & Weakley in 1889, working from offices in the First National Bank Building. He also served as a deacon at First Baptist Church of Birmingham.
Cabaniss maintained his successful practice until his death in March 1936. His wife died two months later.
- Dubose, Joel Campbell (1904) Notable men of Alabama: Personal and Genealogical 2 Volumes. Atlanta, Georgia: Southern Historical Association
- Owen, Thomas McAdory and Marie Bankhead Owen (1921) History of Alabama and Dictionary of Alabama Biography. 4 volumes. Chicago, Illinois: S. J. Clarke Publishing Co.
- Edward Harmon Cabaniss at Findagrave.com