Mordecai (Mordica) Steele was born on February 16, 1834, in Albemarle County, Virginia. Steele worked as a farmer in Huntsville, Alabama, and he may have been owned by Chambers Steele. He married his first wife Louisiana in Limestone County, Alabama, but she died sometime before the war. Steele enlisted in the Union army on February 27, 1864, in Shelbyville, Tennessee, and mustered in as a private in Company H of the 15th USCT Infantry Regiment in Nashville soon after. His enlistment record describes him as 5 feet, 10 inches tall, with black hair, black eyes, and a black complexion. He fell ill during the summer of 1864, and the army deemed him unfit for field service. In response, officials transferred him to Company E of the 101st USCT Infantry Regiment on November 21, 1864, and he spent the rest of the war performing garrison duty. He became a corporal on April 29, 1865, but he was reduced to the ranks almost immediately.

Steele married Amanda Dabine on November 1, 1865, in Nashville, and he mustered out on January 21, 1866. Steele settled in Chattanooga after the war, and he spent the following years working as a laborer and moving between Tennessee and Alabama. He and Amanda had two children together: Samuel, born February 15, 1872; and Sarah A., born October 20, 1874. Amanda died on January 4, 1904, and he married Mary Townsend in 1906. She died in 1910. After his military service, Steele suffered from rheumatism, heart trouble, partial loss of sight, and jaundice. He applied for a pension in 1883, and by 1900, he was receiving $8 a month. He died of asthma on April 9, 1913, in Nashville, Tennessee. Following his death, a woman named Susan Steele applied for a pension, claiming to be his widow. It is unclear if she and Steele had ever been married, and the government ultimately rejected her application.