Entered service from Colorado. Member Company A, 1st Colorado Volunteers. On night before capture of Manila led a strong detachment past entrenchments and threw up temporary earthworks for use of troops the next day and also worked until early morning hours cutting a road through the brush next to the seashore to allow men to advance on Fort San Antonio de Abad without being in full view of the enemy. Killed in action in offensive toward Malolos. Death spurred the men of his company to charge enemy trench line that caused strongly protected enemy line to flee. Was senior line officer of the regiment and generally known as one of its best-posted officers, often taking command of 1st Battalion during emergencies. Funeral on February 11, 1900 drew estimated 20,000 people, largest in Colorado history to that time.

The John S. Stewart Camp No. 3 was organized and instituted in December 1905 in Pueblo Colorado and named in his honor.  At the start of the war with Spain, he was a member of the Colorado National Guard and on May 1st 1898 he was mustered into service as Captain of Company A.  His remains were brought home and he was buried at the Roselawn Cemetery in Pueblo.