Leopold Mayer was born in Abenheim, Germany, on March 3, 1827, the son of Aaron Mayer (d. 1871). After attending a Catholic seminary (despite being Jewish), he taught school from 1846-1849. In November 1849, he left with his father and sister for the United States, and they arrived in Chicago, Illinois, in April 1850. There, Mayer taught languages and religion, helping to found a religious school and the Hebrew Benevolent Society. He supported the establishment of the reform congregation that became the Chicago Sinai Congregation in 1861, and he served as county supervisor from 1868-1869. In 1854, Mayer became a bank clerk, and he established a firm with O. R. W. Lull in 1855; the business later became Leopold Mayer and Son, which 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 Flomersheim (or Mannheim), Germany, who had also immigrated to Chicago. 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 meat and seafood supply store in Chicago. They had three children: Felix J. (b. October 18, 1886), Elsie (b. April 28, 1889), and Regina (b. December 11, 1894).