Elias D. Leach was born near Youngstown, Ohio, on March 26, 1823, the son of Benjamin Leach and Hannah Raynor. He had at least two brothers, Jacob B. Leach and S. F. Leach. In 1842, he moved to West Greenfield, Pennsylvania, where he studied medicine with a doctor named Packard. In 1844, Elias Leach traveled to Cleveland, Ohio, where he began his formal medical education at Western Reserve College (now Case Western Reserve University), where he received his medical degree in 1848. From 1848 to 1853, he practiced medicine in Virginia, Illinois, and Frederick, Illinois, and in 1853 he moved to Rushville, Illinois, where he joined Little, Ray & Co., a mercantile firm. He worked for the firm until 1863 and again between 1880 and 1890. Leach married his third wife, Harriet Jane Patteson, on December 4, 1856. They had three children: Junius (1858-1887), Warren, and Lawrence. Elias D. Leach died in September 1890.