Daniel R. Forgus was born around 1827 in New Jersey to John and Priscilla Forgus. His father died sometime before 1850. They lived in Greenwich, New Jersey, and by the 1850s, Forgus was working as a boatman and a laborer. He married Martha Brotzman on November 22, 1852, in Easton, Pennsylvania. Martha probably died sometime before 1870.
Forgus enlisted in the Union army on May 23, 1861, and he mustered in as a private in Company G of the 1st New Jersey Infantry five days later. The regiment took part in the First Battle of Bull Run, the Second Battle of Bull Run, the Battle of Antietam, the Battle of Fredericksburg, the Battle of Gettysburg, and the Overland Campaign. In November 1861, he observed that "there is a great many [New Jersey soldiers] that there simpithy is with the South but thank god not quite all I for one doant and never will as long as I keep what littel cence Ive got." He was promoted to corporal in late 1861 and then to sergeant on September 14, 1862. On January 31, 1865, he was promoted to 2nd lieutenant and transferred to Company F of the 4th New Jersey Infantry.
Forgus worked as a shoemaker in Delaware, New Jersey, after the war. He moved to Durham, Pennsylvania, sometime in the 1870s. He applied for a federal pension in February 1881 and eventually secured one. He died on May 8, 1883, in Philadelphia, Pennsylvania.