Sponsored Topics. Brookfield is a city in Linn County, Missouri, United States. The population was 4,542 at the 2010 census. Brookfield is located at 39°46′59″N 93°4′26″W / 39.78306°N 93.07389°W / 39.78306; -93.07389 (39.783155, -93.073871). According to the United States Census Bureau, the city has a total area of 4.3 square miles (11.1 km²), all of it land.