Marc was born Markus to a Jewish family in Prague, Bohemia. He emigrated to the United States in 1846 with his mother Judith Eidlitz after the death of his father Abraham. Having served a four-years apprenticeship, he set up in business for himself in 1852, the year of his marriage.
Through his influence, the Masons Builders' Association of New York played a major role in founding the National Association of Builders. In New York he was President of the Building Trades' Club and of the Germanic Savings Bank.
Selected commercial commissions
The following structures erected by Eidlitz were all in New York City, unless otherwise identified.
- A mission on 20th Street, commissioned by William Colgate
- Broadway Tabernacle (1857–58)
- Lord and Taylor Building, Broadway and Grand Street
- The German Hospital (now Lenox Hill Hospital at another site)
- Saint Vincent's Hospital
- Home of the Sisters of Bon Secours
- Church of the Incarnation, Madison Avenue and 35th Street
- Temple Emanu-El, former building at Fifth Avenue and 43rd Street
- St. George's clergy house, 16th Street
- Astor Library
- Steinway Hall
- Gallatin Bank
- Metropolitan Opera House (J. Cleaveland Cady, architect, 1883)
- Seamen's Savings Bank
- Eagle Fire Insurance Company
- Schermerhorn Building, 376 Lafayette Street (Henry J.Hardenbergh, architect, 1889)
- Astor Building
- Eden Musée
- Western Electric Building
- Lancashire Fire Insurance Company
- Empire Building, Broadway and Rector Street
Kathryn Holliday, Leopold Eidlitz: Architecture and Idealism in the Gilded Age (New York: W.W. Norton, 2008)
- Biographical information is drawn from his obituary, The New York Times, 16 April 1892.