We know Jacob as the son of John from his presence in his father’s 1850 and 1860 household. He is designated P5c1a.

I did find him in 1880 living alone in Minneapolis. I think Jacob K never married.

His obituary was in the Miffilinburg Telegraph 11 Nov 1898. “Jacob K Mertz, a prominent citizen of Minneapolis died in that city 31 Oct of heart trouble age about 55 years. He was the son of the late John Mertz, dec'd, long time Justice of the Peace in Lewisburg. Jacob was born in Lewisburg. He enlisted in Co D 5th Reg PA Res Corp early in 1861 and was discharged 4 Feb 1863 on account of disability. Afterward he re-enlisted and served again. After the war, he went to Minnesota where he became a prominent member of the GAR. He was buried in St. Paul. Three sisters survive him: Mrs. Kieffer Wolfe of Hartleton, Mrs.Wm Martin of Lewisburg and Mrs. Josa Levers of Milton.”