James Washington Singleton was born on November 23, 1811 at "Paxton" in Frederick County, Virginia, the estate of his father, General James Singleton. After attending the academy in Winchester, Virginia, Singleton moved to Kentucky in 1828. He married Mathilde Caves who died in 1832. Singleton pursued the study and practice of medicine in Kentucky. Later he married Ann Craig of Lexington, Kentucky. About 1834 he settled at Mount Sterling, Illinois. He commenced the study of law in Mount Sterling and was admitted to the Illinois bar in 1841. During these years the Singletons had a son, James Washington, Jr. but he died in infancy. Ann Craig Singleton also died about 1840.

James Washington Singleton began to distinguish himself in public service during the 1840's. In the "war" against the Mormons he was in command of a military company and he was later commissioned a brigadier-general of militia by Governor Ford of Illinois for his services in the Mormon War. He married Parthenia McDonald on April 9, 1844. He had two children by his third wife: Louise(Lily) born in 1857 and James J. Singleton born in 1860. In 1847 he was elected to represent his county in a constitutional convention. He served in the Illinois legislature representing Schuyler(Brown) County from 1850 to 1854. The Singletons moved to Quincy where James Washington practiced law and became active in politics. He served in the state legislature from 1860 to 1862. He also represented Quincy in the state Constitutional convention of 1861.

During the Civil War Singleton may be most accurately characterized as a Peace Democrat who maintained close ties with President Lincoln. He had met Lincoln while he was in legal practice in Illinois in the 1840's. Their friendship lasted until Lincoln's death although they held different positions on the principal political issues of the time. Singleton apparently held informal "negotiations" with several people in Richmond including President Jefferson Davis and General Robert E. Lee. Lincoln did not give official sanction to these talks but was ready to recognize them if satisfactory Confederate proposals should emerge from the negotiations. Singleton died at home on April 4, 1892.