Veterans Administration pension records list an Isaac Barnum who served as a sergeant with Company "E", 12th Rhode Island Infantry.
From the Republican Watchman, Monticello, NY, March 1925: From the Barrington, R.I. News: Isaac Barnum, who a few years ago was one of the best known men in Bristol County, passed away at his home on Maple Avenue Thursday morning in his 83rd year. Mr. Barnum was born in Monticello, N.Y. September 11, 1842. In January 1860 he came with his folks to Nayatt and it was from here that he joined the Ninth Rhode Island Infantry at the outbreak of the Civil War. He saw four months service in this and then was mustered out. He reenlisted a few months later in Company E of the 12th R.I. Volunteers, the color company of the regiment and was advanced to Sergeant. He served in the army of the Potomac under Burnside and was at the battle of Fredericksburg, December 12, 1862. In 1863, the company was detached from the Army of the Potomac and sent to Lexington, Kentucky. They served out their time here by breaking up the small bands which infested the mountain districts of the State. On the way home the company stopped at Cincinnati and offered their services as guard for this Ohio city. In August 1863 he was mustered out in Providence. It was on Christmas Day of the following year that he married Edna A. Viall, daughter of the late George K. and Ardella Richmond Viall. They were married at the home of the bride. Four children were born to them, two of whom have passed away. Their daughter Mabel, the day she was to have graduated from the Providence high school May 30, 1887 in her 19th year, while their only son George died in December of 1896 aged 18 years. While Mr. and Mrs. Barnum were on their wedding trip Mr. Barnum’s partner George R. Viall met with a serious accident cutting himself so badly that he was laid up for a year.
Mr. Barnum later took over the business selling out the grocery and keeping the market. The business grew and prospered. Later he opened a branch store in Nayatt. Mr. Barnum went into business with his nephew, I. F. Viall in West Barrington. He also conducted a slaughter house and ran a butcher cart through the surrounding territory. In 1914 he decided to retire from business and since then has been engaged in no active business pursuits. December 25, 1916, Mr. and Mrs. Barnum celebrated their golden wedding day. Mrs. Barnum died in 1919. Mr. Barnum is survived by two daughters, Julia Dunbar and Miss Letitia Barnum, both of Barrington.