John Thomas grew up in a family of patriotic people: his father, John Thomas Sr.; mother, Jane Black Thomas and seven siblings. His three brothers and four sisters were Robert, who was killed in Roebuck's defeat at the Battle of Mudlick's Creek in 1781; Abram, wounded at Ninety-Six, was taken prisoner and died in the enemy's hands; William, who assisted his family in defending their home; Martha, who married Josiah Culbertson; Ann, the wife of Joseph McJunkin, who greatly contributed to the success of the battles at Hanging Rock, Musgrove's Mill, Blackstock's Fort and the Cowpens; Jane, who married Capt. Joseph McCool; and Letitia, wife of Maj, James Lusk. All were active in the Revolutionary War.

Col. John Thomas Jr. served with his father, Col. John Thomas Sr., in the Spartan Regiment of South Carolina. The original Spartan Regiment was organized Aug. 21, 1775 at Wofford's Iron Works with Col. Thomas Sr. as its first commander. The regiment held its first muster, or review, at Col. Thomas' home on the Fair Forest Creek. It was reorganized in the summer of 1780. It was a volunteer organization whose officers and men served without pay and without provisions. ...

When his father was taken prisoner in 1780 for 14 months, Col. John Thomas Jr. succeeded him in the command of the Spartan Regiment, which he led at the Battle of the Cowpens and elsewhere. He is known as the "Hero of Cedar Springs." The first Battle of Cedar Springs happened just a few miles away from where the town of Glendale, South Carolina, is today. The battle was a Patriot victory that took place on July 13, 1780, in modern day Spartanburg County. A Tory force from the British outpost at Ninety-Six tried to surprise a Patriot force under Col. John Thomas Jr. camped at Cedar Springs.

At the time, Thomas' father was being held as a British prisoner at Ninety-Six and his mother was visiting her husband. His mother overheard some of the Tory wives discussing the surprise attack that was supposed to be made against Cedar Springs. She left early the next day and rode about 60 miles to Cedar Springs to warn her son and his soldiers. With this warning, the Patriots set up an ambush. The Tories rode into what they thought was a sleeping camp. Instead, many were killed or wounded by the waiting Patriots.

Col. John Thomas Jr. was with Gen. Sumter in 1781 and fought in several important engagements. He served in the Light Dragoons, with the Civil Service and on the jury in the Ninety-Six District, South Carolina.

After the Revolutionary War Col. John Thomas Jr. came to Shiloh, Illinois, with his family. He was very active is establishing the Shiloh Methodist Church. He was made treasurer of the Territory. Later he became the first treasurer or the State of Illinois and died on July 29, 1819 while in office. He is buried in the Shiloh Methodist Church yard.