Nelson served in the Mexican War of 1846-48 as a young man. He was a Private in Company C and Company F of the 1st Illinois Infantry (Newby’s). Although no 1850 census listing has been found for Nelson, he was in Missouri by 1851. He married first on June 2nd, 1851, in Paris, Monroe, Missouri to Martia Balthorpe (1829 Virginia - 1853 Missouri), with whom he had one son, John. Nelson married a second time on February 20th, 1858, in St Louis, Missouri, to Mary Keever Gordon Lyons (29 June 1839 Bolton, England - 23 Oct 1908 Pittsburgh, Pennsylvania), with whom he had 12 known children: J. Sylvester, Norman (died young), Nelson (died young), Margaret Minerva, Elvira, Oscar Humphrey, Helen D. (died young), Harriet May (Arthur) Weaver, Edwin Simeon, Norman Nelson, Raymond Oliver, and Frank Goodrich Barnum (died young). The 1900 census indicates that his second wife Mary was the biological mother of 13 (with 6 still living. It’s unclear who was the 13th child. Nelson and Mary are recorded in the 1860 census in St. Charles, Illinois, returned to Missouri for a while, and relocated to LaPorte, Indiana before 1870. (FamilySearch has poorly transcribed their surname as Burnusn (sic) on the 1870 census). A family source records his name as Nelson William or William Nelson but his grave marker shows Nelson N.
Headstones Provided for Deceased Union Civil War Veterans, 1879-1903. Name: Nelson Barnum; Pvt, Co F, 1st Regt, Illinois Volunteer Infantry - Mexican War; Cemetery: Patton; At: La Porte, Indiana; Date of Death: 13 Aug 1891; Headstone supplied by: Vt. Marble Co., Proctor, Vt. Contract Nov. 30, 1894.