Barnes City is a city in Mahaska and Poweshiek counties in the U.S. state of Iowa. The population was 176 at the 2010 census.
Barnes City is located at 41°30′30″N 92°28′8″W (41.508248, -92.468980).
According to the United States Census Bureau, the city has a total area of 0.59 square miles (1.53 km2), all land.
As of the census of 2010, there were 176 people, 88 households, and 47 families living in the city. The population density was 298.3 inhabitants per square mile (115.2/km2). There were 99 housing units at an average density of 167.8 per square mile (64.8/km2). The racial makeup of the city was 99.4% White and 0.6% Native American.
There were 88 households, of which 17.0% had children under the age of 18 living with them, 42.0% were married couples living together, 5.7% had a female householder with no husband present, 5.7% had a male householder with no wife present, and 46.6% were non-families. 40.9% of all households were made up of individuals, and 13.6% had someone living alone who was 65 years of age or older. The average household size was 2.00 and the average family size was 2.68.
The median age in the city was 49.2 years.