James Jackson Diamond, secessionist politician and soldier, was born on July 16, 1827, in De Kalb County, Georgia, the eldest of six sons born to James and Nancy Diamond. He attended Maryville College in Tennessee and practiced law in Georgia. He moved to Texas before the Civil War. He raised cotton in the Red River Valley and subsequently settled near Whitesboro in Grayson County. Diamond became a leading spokesman for Southern rights and views. He was a delegate from Texas to the 1860 Democratic national convention in Charleston, South Carolina, and, after the nomination of Stephen A. Douglas for president, bolted the convention.
Upon the election of Abraham Lincoln in November 1860 Diamond helped call a public meeting of citizens from Cooke and Grayson counties. The gathering convened at Whitesboro on November 23 and named Diamond chairman of the committee that offered resolutions calling upon Governor Sam Houston "to ascertain the will of the people...by convention, or otherwise" on the question of secession. As one of the two delegates from Cooke County, he voted with the majority at the Secession Convention to sever the political ties of Texas with the Union. He was appointed a member of the convention's Committee of Public Safety, which served, in effect, as the interim government of Texas until March 2, 1861, when the referendum on the Ordinance of Secession was officially endorsed.
In May of 1861 Diamond was elected captain of a company of state militia. He joined Col. William C. Young's Eleventh Texas Cavalry, organized in July 1861, as a captain, was quickly promoted to lieutenant colonel, and later held the rank of colonel. When the regiment was reorganized in May, 1862, he was not reelected colonel and returned to Texas. He was one of the organizers and managers of the "citizens' court" formed in Gainesville in October 1862, which brought to trial and hanged thirty-nine persons accused of participating in the supposed "peace party conspiracy" (see GREAT HANGING AT GAINESVILLE). Later in the war he served as adjutant to the Twenty-first Brigade of Texas militia.
After the war he moved to Houston and assumed the editorship of the Houston Dispatch. He died in Houston on October 9, 1867, during the yellow fever epidemic, and is probably buried in an unmarked grave in the Old City Cemetery. He was married twice, first to Adeline E. Holmes, then to Amanda Jourdan Finley. He had several children, some of whom died with him in the yellow fever epidemic. William W., George W., and John R. Diamond were brothers.