Marshalltown is a city in Marshall County, Iowa and is the county seat of the county. With a population of 27,591 at the 2020 census, it is the 1…Marshalltown is a city in Marshall County, Iowa and is the county seat of the county. With a population of 27,591 at the 2020 census, it is the 16th largest city in the state. Marshalltown is home to the Iowa Veterans Home and Marshalltown Community College. Marshalltown is known as the Paris of the Prairie.