Leopold Mayer was born in Abenheim, Germany, on March 3, 1827, the son of Aaron Mayer (d. 1871). After attending a Catholic seminary, he taught school in Germany from 1846 to 1849. In November 1849, he, his father, and his sister left for the United States, and they arrived in Chicago, Illinois, in April 1850. There, Mayer taught languages and religion at various institutions. He helped organize the Hebrew Benevolent Society in 1851, supported the establishment of the reform congregation that became the Chicago Sinai Congregation in 1861, and served as county supervisor from 1868 to 1869. Mayer became a bank clerk in 1854, before establishing his own banking firm with O. R. W. Lull in 1855. The business changed its name to Leopold Mayer and Son following Lull's death, and later merged with the Garden City Bank and Trust Company in 1900. On December 4, 1853, Leopold Mayer married Regina Schulz (December 25, 1833-February 7, 1893), a native of Mannheim, Germany, who emigrated to Chicago in 1852. They had eight children: Nancy (November 6, 1854-November 29, 1891), Nathaniel A. (October 30, 1856-December 29, 1924), Rose (February 15, 1859-January 9, 1929), Grace Aguilar (May 27, 1861-January 17, 1923), Amelia (b. April 21, 1863), Julia (February 13, 1865-January 1866), Ida (b. August 12, 1867), and Flora (b. November 2, 1869). Leopold Mayer died on December 15, 1903.
Amelia Mayer married Jacob Henry Mahler (January 14, 1853-May 4, 1917), who owned a store in Chicago. They had three children: Felix J. (b. October 18, 1886), Elsie (b. April 28, 1889), and Regina (b. December 11, 1894).