Armstrong was born in 1821 in Greene County, Pennsylvania. He died March 23, 1899, at Chetek, and was buried in the nearby Twin Lakes Cemetery in Chippewa Co., Wis. His military style gravestone is inscribed "Armstrong Moore 6th Wis. Batt'y."

Armstrong was married four times. His first marriage was to Anna Hamilton in Peru, Wis. They separated in about 1876, at Spring Green, Sauk County, Wis. No known divorce. She died in about 1893, at the home of her daughter, Eliza Petteplace, at Smith Center, Kansas. Their children were:

Mary, b. 21 Nov;
Eliza, b. 2 May;
Matilda A., b. 18 Jun;
Thompson P., b. 2 May;
Pricilla, b. 29 Jan;
Winfield, b. 20 Aug;
Edward, b. 20 May.

The children's names and the month and day of their birth, but not the year, were taken from a form in Armstrong's pension file at the National Archives.

Armstrong's second marriage was to Ellen Van Valkenburg. Nothing about her is known other then that they lived together until she died near Farley, Dubuque County, Iowa. No known children.

Armstrong's third marriage was to Elizabeth Harris, who died March 1, 1886, at Chetek, Barron County, Wisconcin. Her place of burial is unknown. No known children.

Armstrong's fourth marriage was to Mrs. Sidney A. Haye, on April 18, 1886, at Chetek. She survived her husband, but her date and place of death and burial are unknown. No known children.

Armstrong was a Civil War veteran of the 6th Independent Battery, Wis. Light Artillery. He enlisted Nov. 1, 1861, at Racine, Wis., to serve three years as a Private in the 6th Independent Battery of Wis. Light Artillery. At that time he was 40 years of age. His muster in date at Racine was given as October 1, 1861, which may be in error, since it predates his enlistment date.

On the Battery Special Muster Roll of April 19, 1863, it was noted that Armstrong was sick in the hospital at Memphis, Tenn. On the Battalion Muster Roll of July/August, 1863, it was noted that he was absent on furlough. On the Battalion Muster Roll of July/August 1864, it was noted that he was charged 45 cents for one canteen. On the Battalion Muster Roll of Jan/Feb., 1864, it was noted that he owed the U.S. $0.62½ for transportation while on furlough. On Oct. 10, 1864, he was discharged with the Battery at Madison, Wisconsin.

After his discharge, Armstrong returned to Wisconsin, where he resided in Sauk and Crawford Counties, except for three years when he resided in Iowa. On Aug. 17, 1882, he was known to have lived in Soldiers Grove, Crawford County, Wisconsin. On an unknown date he moved to Chetek, Barron County, Wisconsin.