Jacob B. Weaver was born in 1822 in Franklin County, Pennsylvania.
Jacob left Pennsylvania and moved west, eventually settling in Michigan sometime before the war broke out.
He was a 39-year-old farmer possibly living in Montcalm County (or perhaps in Grand Rapids) when he enlisted in Company D on May 13, 1861. He was reported missing in action on June 1, 1862, at Fair Oaks, Virginia, but was returned to the Regiment on November 26, 1862, at Warrenton, Virginia. He was a nurse in the Division hospital in May of 1863 and a nurse at the hospital in Alexandria, Virginia from June through July.
Jacob had apparently returned to duty by the time he reenlisted on December 23, 1863, at Brandy Station, Virginia, crediting Boston, Ionia County. He was presumably on veteran’s furlough in January of 1864, and probably returned to the Regiment on or about the first of February.
Jacob was transferred to Company A, Fifth Michigan infantry upon consolidation of the Third and Fifth Michigan Regiments on June 10, 1864, and was killed in action June 18 near Petersburg, Virginia. He was first buried on the Henry Bryan property near Meade Station, Virginia, but reinterred in City Point National Cemetery: grave 2483.
No pension seems to be available.