Elon Farnsworth's uncle, John F. Farnsworth, served in the United States House of Representatives from Illinois between March 4, 1857 and March 3, 1861 and again between March 4, 1863 and March 3, 1873. John Farnsworth was a Union Army colonel who also commanded cavalry brigades (September 1862 to February 1862) and was nominated for appointed to the grade of brigadier general (November 1862). His appointment also was not confirmed by the United States Senate after the nomination was ordered returned to President Lincoln on February 12, 1863.