William C. Parker was a member of the 58th Regiment Arkansas Militia when the war started. This was the militia regiment of that portion of Franklin County south of the Arkansas River, and now encompassed in Logan County. During the regiment's annual muster for inspection and drill, held February 22 to March 21, 1862, he was present as first lieutenant of Company E.

He enlisted in Co. E, 1st Arkansas Cavalry, U.S. Volunteers, in Franklin county, Arkansas, July 3, 1862; age 23; mustered into service at Springfield, Missouri, July 10, 1862, for three years; appointed sergeant, July 10, 1862; reduced to ranks at his own request, August 1, 1862; present, December 31, 1862; present, February 28, 1863; detailed on recruiting service for the 1st Arkansas Infantry, March 1, 1863; discharged to accept appointment in the 1st Arkansas Infantry, April 1, 1863.

He was appointed captain, Co. H, 1st Arkansas Infantry, U.S. Volunteers, March 25, 1863; age 24; remarks, promoted from private, Co. E, 1st Arkansas Cavalry Volunteers; slightly wounded in the head at Fayetteville, Arkansas, April 18, 1863; present, April 30, 1863; present, June 30, 1863; present, August 31, 1863; present, October 31, 1863; detailed on recruiting service for the 4th Arkansas Cavalry, November 1, 1863; absent on detached service, December 31, 1863; present, February 29, 1864; absent sick, April 30, 1864; returned to duty, June 26, 1864; present, June 30, 1864; remarks, returned and assumed command of company, having been absent sick; present, August 31, 1864; present, October 31, 1864; present, December 31, 1864; present, February 28, 1865; present, April 30, 1865; furloughed for fifteen days to visit DeValls Bluff, Arkansas, per Special Orders, No. 67, dated at Headquarters, 3rd Division, 7th Army Corps, Fort Smith, Arkansas, May 12, 1865; detailed as witness in court-martial at Little Rock, Arkansas, June 11, 1865; mustered out with the regiment at Fort Smith, Arkansas, August 10, 1865.