Hamburg is a city in Fremont County, Iowa, United States, that is the most southwestern city in Iowa, hugging the borders of Missouri to the south and Nebraska to the west. It is situated between the Nishnabotna and Missouri rivers. The population was 1,187 at the 2010 census. It derives its name from the German city of Hamburg.
The city is less than a quarter mile from the Missouri state line. The first settlers in the community were people who actually thought they were settling in Missouri following the Platte Purchase of former Indian territory there across the state line opened up settlement. The first formal settlement in the Hamburg vicinity were by the brothers James McKissick, Cornelius McKissick, Daniel McKissick who established McKissick's Grove. A survey was made when Iowa entered the union in 1846, and only then did the settlers discover that they were in Iowa and not Missouri.
The brothers were also involved in another border irregularity when they bought McKissick Island a mile south of Hamburg. They thought at the time the island in the Missouri River was attached to Nebraska territory. The river changed course in 1867 resulting in the island becoming physically attached by dry land to Missouri and cut off from Nebraska by the main channel.