Grantum Oblinger was born around 1846 in Pennsylvania to Francis and Catherine Oblinger. His father was a laborer who owned $300 of real estate in 1850. By 1850, he was working as a cooper in Mount Bethel, Pennsylvania. He married Elizabeth Rasley around 1850, and they had at least five children: Alice, born around 1851; Francis, born around 1854; Eliza, born around 1856; Daniel, born around 1859; and Clinton, born around 1861. They moved to New Jersey sometime in the 1850s.
Oblinger enlisted in the Union army on September 13, 1861, and mustered in as a private in Company K of the 8th New Jersey Infantry later that day. The regiment took part in the Battle of Seven Pines, the Seven Days’ Battles, the Second Battle of Bull Run, the Battle of Fredericksburg, the Battle of Chancellorsville, and the Battle of Gettysburg. He died of chronic diarrhea in Washington, D.C., on September 25, 1863.