Denmark once had a post office called Merritt, named for the Merritt family who were the first settlers there. A post office was established under the name Marits in 1833, and remained in operation until 1907. Besides the post office, Denmark once contained a church and country store.
- U.S. Geological Survey Geographic Names Information System: Denmark, Ohio
- History of Morrow County and Ohio: Containing a Brief History of the State of Ohio. O.L. Baskin & Company. 1880. p. 476.
- "Morrow County". Jim Forte Postal History. Archived from the original on 22 December 2015. Retrieved 15 December 2015.
- Baughman, Abraham J.; Bartlett, Robert Franklin (1911). History of Morrow County, Ohio: A Narrative Account of Its Historical Progress, Its People, and Its Principal Interests. Lewis Publishing Company. p. 388.