David F. Ilgenfritz was born on March 27, 1835, in Pennsylvania, to Samuel Ilgenfritz and Lydia Imfelt. His father was a farmer in York County, Pennsylvania, who owned $9368 of real estate and $2660 of personal property in 1860. Ilgenfritz married Kathryn Ann Curran around 1859, and they had at least eight children: Sarah, born around 1859; Lilly, born around 1860; David, born around 1861; George, born around 1866; Anna, born around 1870; Samuel, born around 1872; John, born around 1876; and Margaret, born around 1879. In 1860, he was working as a blacksmith in York, Pennsylvania. He enlisted in the Union army on April 20, 1861, and mustered in as a private in Company A in the 16th Pennsylvania Infantry. According to his service records, he was 5 feet, 4 inches tall, with dark hair and dark eyes. He mustered out in Harrisburg, Pennsylvania, on July 30, 1861. He re-enlisted on August 25, 1862, and mustered in as a private in Company F of the 1st Pennsylvania Cavalry. He mustered out on May 27, 1865.
Ilgenfritz returned to York County after the war and began working as a blacksmith. He applied for a federal pension on November 12, 1883, and eventually secured one. According to the 1890 veterans census, he was suffering from an unspecified “rupture.” He died in York, Pennsylvania, on March 23, 1903.