Theophilus H. Vanaman was born to Joseph and Catherine (Hankins) Vanaman in 1830 at Maurice River, Cumberland County, New Jersey. He married Zada (sometimes listed as Sarah) Lee on Dec 18, 1852.

Theophilus Vanaman enlisted as a Private on Sept 2, 1862 in Co G, 25th NJ Infantry for 9 months. He was 32 years old at enlistment. He mustered into his unit on Sept 8 at Beverly, NJ.

The 25th NJ moved to Washington DC on Oct 10, 1862, where it went into camp on East Capitol Hill and was on picket duty at Fairfax Seminary. Part of Burnside's IX Corps, the 25th NJ participated in the Battle of Fredericksburg in Dec and Burnside's infamous "Mud March in Jan 1863. On Feb 11th, it moved to Newport News, VA, and was on duty there until March 13, when it moved to Suffolk, VA. The regiment served on picket duty at Fort Jericho in the Suffolk defenses. This fort was located just south of the Seaboard and Roanoke Railroad and west of Jericho Creek/canal. (This neighborhood of Suffolk is still called "Jericho.")

While at Fort Jericho, PVT Theophilus Vanaman contracted typhoid fever and died on March 28th, 1863 just before the "Siege of Suffolk." The diary of the regimental chaplain, Francis E. Chapman, mentions PVT Vanaman's burial in the PM on March 29th.

Theophilus Vanaman left behind his wife, Zada Lee, and five small children under the age of 10.