Watson Harper Gilbert was born in Morristown, Illinois, the son of Rev. Joseph Gilbert, a Methodist minister, and Nancy Caldwell Gilbert. He lived in Kewanee, Illinois at the time of his enlistment in March of 1864.

He served with Company A of the 42nd Illinois Volunteer Infantry from April, 1864 until January 1866.

After returning to Kewanee when he was discharged in 1866, he was engaged in the farm implement business until moving to Iowa with his then widowed mother in 1869. There he worked as a music dealer and teacher. He married Aurelia White in Camanche, Iowa, in 1869, and they later moved to Clinton, Iowa. They had one son, Charles Raymond. Watson died on Christmas day, 1883 -- only 37 years old. He was buried in Rose Hill Cemetery, Camanche, Iowa.