John S. Simonson was born on June 2, 1796, in Fayette County, Pennsylvania. He grew up there and reportedly received a “limited education.” He served along the “Niagara frontier” during the War of 1812 and took part in the Battle of Lundy’s Lane in July 1814. He settled in Charlestown, Indiana, around 1817, and he married Elizabeth Watson on May 3, 1820.
He became sheriff of Clarke County, Indiana, in 1822 and won reelection two years later. He secured a seat in the state senate in 1828 and became a justice of the peace in 1830. He returned to the state legislature in 1841 and became state speaker of the house four years later. When the Mexican American War erupted, he served as a captain in the United States army under General Winfield Scott. He participated in the siege of Vera Cruz, the Battle of Cerro Gordo, the Battle of Cherubusco, and the Battle of Chepultepec. He remained in the army after the war and spent the ensuing years in Oregon, Texas, and New Mexico.
He was promoted to colonel of the 3rd United States Cavalry in May 1861, but the army placed him on the retired list in September 1861. He served as superintendent of the volunteer recruiting service in Indiana during the Civil War. He returned to Charlestown after the war, and by 1880, he was suffering from piles. He died on December 5, 1881.