According to Widow's Pension, Arnold died March 11, 1863. He presumably died from disease contracted during the Civil War. State records in Illinois indicate that Arnold was discharged in St. Louis, MO due to a disability.
The pension paperwork lists three children: Marion Pleasant age 6 Angeletta Elen age 2 John Andrew age 1 month
Wikiepedia-The 97th Illinois Infantry was organized at Camp Butler, Illinois and mustered into Federal service on September 16, 1862. The regiment was mustered out on July 29, 1865.The regiment suffered 2 officers and 28 enlisted men who were killed in action or who died of their wounds and 200 enlisted men who died of disease, for a total of 233 fatalities.
Familysearch.org -The 97th Regiment, Illinois Infantry was organized at Camp Butler, Illinois, and mustered in September 16, 1862. It moved to Mobile May 11, thence to Galveston, Texas, and had duty there until July. It mustered out July 29, 1865
U.S. Civil War Soldiers Name: Arnold Hinman Residence: Alton, Illinois; Enlistment Date: 13 Aug 1862 Side Served: Union; State Served: Illinois Service Record: Enlisted as a Private on 13 August 1862. Enlisted in Company G, 97th Infantry Regiment Illinois on 16 Sep 1862. Received a disability discharge from Company G, 97th Infantry Regiment Illinois on 24 Feb 1863.
Illinois Civil War Detail Report (Illinois State Archives) Arnold Hinman Rank: PVT CO G 97 IL US INF Residence: Alton, Madison Co, IL Age 29, Height 5"5'; Hair: Brown; Eyes: Hazel; Hair: Dark Married, Occupation; Farmer Nativity: Florence, Indiana Joined: Aug 13, 1862 Madison Co, IL; Joined by: J Trible; 3 years Camp Butler, IL Discharged Feb 24, 1863 at St. Louis, MO for disability
Civil War Pension Index (Ancestry) Arnold Hinman G 97 Ill Inf Angeline Hinman-Widow App: 21294; Date Filed: May 13, 1863