Alleman is a city in Polk County, Iowa, United States. The population was 423 at the 2020 census. It is part of the Des Moines–West Des Moin…Alleman is a city in Polk County, Iowa, United States. The population was 423 at the 2020 census. It is part of the Des Moines–West Des Moines Metropolitan Statistical Area. Alleman was named for early settler John L. Alleman. It did not incorporate as a city until May 18, 1973, making it the most recent city to incorporate in Polk County.