Denmark is an unincorporated community and census-designated place in northeastern Lee County, Iowa, United States. It lies along Iowa Highway 16, north of the city of Fort Madison, the county seat of Lee County. Its elevation is 722 feet (220 m) above sea level. Although Denmark is unincorporated, it has a post office with the ZIP code of 52624, that opened on April 7, 1846. The community is part of the Fort Madison–Keokuk, IA-MO Micropolitan Statistical Area. As of the 2010 Census the population of Denmark was 423.
Denmark was laid out circa 1837.
In 1836, four families emigrated from the town and church of New Ipswich, NH to Denmark in what was then Wisconsin Territory, now in Iowa. Within a short time they were followed by eight other families. They all carried with them the same standard of right living and wise planning for the best interest of those who should come after them that they had known in New Ipswich. Those who "laid out the town of Denmark, which is three-fourths of a mile square, into town lots for building, donated one-half of those lots to the purpose of Education." In the building of a church and of an academy they followed as closely as possible the example set by the founders of New Ipswich. The church set up by the settlers is the oldest Congregational church in Iowa.