Born near Nicholasville, Kentucky, Singleton attended the common schools. He was graduated from St. Joseph's College, Bardstown, Kentucky, and from the law department of the University of Lexington. He was admitted to the bar in 1838 and commenced practice in Canton, Mississippi. He served as member of the State house of representatives in 1846 and 1847. He served in the State senate 1848-1854.
Singleton was elected as a Democrat to the Thirty-third Congress (March 4, 1853 – March 3, 1855). He was an unsuccessful candidate for reelection.
Singleton was elected to the Thirty-fifth and Thirty-sixth Congresses and served from March 4, 1857, until January 12, 1861, when he withdrew. He served as a representative from Mississippi in the First Confederate Congress and Second Confederate Congress from 1861-1865.
Singleton was elected as a Democrat to the Forty-fourth and to the five succeeding Congresses (March 4, 1875-March 3, 1887). He was not a candidate for renomination in 1886. He died in Washington, D.C., January 11, 1889. He was interred in Canton Cemetery, Canton, Mississippi.
de:Otho Robards Singleton