Thomas was only four years old when his father died, and he started work young to help his widowed mother.

[7] Governor Erastus Fairbanks called an extra session of the State Legislature on April 23, 1861, which Thomas attended.

He was a member of the Ways and Means committee, which intended to report out a bill appropriating half a million dollars for military purposes.

Thomas presented an impassioned speech supporting an amendment that doubled the amount to one million dollars.

During this period, the 8th Vermont participated in the Occupation of New Orleans, and battles at Raceland,[17] Boutte Station,[18] Bayou des Allemands,[18][note 3]Bisland, and Port Hudson.

In July 1864, a portion of the XIX Corps, including the 8th Vermont, was transferred to the eastern theater of the war.

They arrived at Fortress Monroe just in time to join the VI Corps in the Shenandoah Valley, and participate in Major General Philip Sheridan's campaign against the Confederacy's Jubal Early.

In 1892 he received the Medal of Honor for "distinguished conduct in a desperate hand-to-hand encounter, in which the advance of the enemy was checked," at Cedar Creek on October 19, 1864.

General Thomas started the war as a Democrat, but by the time he returned home, he was a Republican.

He was Companion #09174 of the Military Order of the Loyal Legion of the United States, or MOLLUS, through its Vermont Commandery.

Citation: The President of the United States of America, in the name of Congress, takes pleasure in presenting the Medal of Honor to Colonel (Infantry) Stephen Thomas, United States Army, for extraordinary heroism on 19 October 1864, while serving with 8th Vermont Infantry, in action at Cedar Creek, Virginia, for distinguished conduct in a desperate hand-to-hand encounter, in which the advance of the enemy was checked.