Isaac Fehl was born on April 27, 1836, in Pennsylvania to Peter and Elizabeth Fehl. His father was a farmer who owned $3,000 of real estate and $750 of personal property by 1860. He was baptized in a Lutheran church in Arendtsville, Pennsylvania, on August 14, 1836. Fehl grew up and attended school in Menallen, Pennsylvania, and by 1860, he was working as a farm laborer in Latimore, Pennsylvania.
Fehl supported the Democratic Party during the war. He was apparently skeptical of the Lincoln administration, believing they were fighting to abolish slavery rather than to preserve the Union. He married Martha McBeth around 1862, and they had at least two children: Martin, born around 1869; and Peter, born around 1876. They lived in South Newton, Pennsylvania, and Fehl worked as a laborer. By 1870, they owned $1,350 of real estate and $150 of personal property. His wife died in the early 1900s, and by 1910, he was living with his son Martin in Newton, Pennsylvania. He died of “chronic bronchitis and general debility” in South Newton on February 5, 1915.