Plainfield is a city in Bremer County, Iowa, United States. The population was 393 at the 2020 census, a decrease of 45, or 10.3%, from 438 in 2000. It is part of the Waterloo–Cedar Falls Metropolitan Statistical Area. The Plainfield post office was established in 1868.
Geography
According to the United States Census Bureau, the city has a total area of , all land.