Fairplain Township is a civil township of Montcalm County in the U.S. state of Michigan. The population was 1,802 at the 2020 census. The Fenwick post office, with ZIP code 48834, serves the southeastern portion of Fairplain Township as well as portions of surrounding townships. Fenwick was founded in 1872 by B. C. Loree, who named it after his home town, Fenwick, Ontario. A post office opened on April 28, 1873, with James R. Hall as its first postmaster. It was platted and recorded on May 22, 1874, by S. C. Alderman for the proprietors Simon M., Sarah, and David Griswold. thumb|
Geography
Fairplain Township is in southern Montcalm County and is bordered to the south by Ionia County. State highway M-57 crosses the central part of the township, leading west to Greenville and east to Carson City.
According to the U.S. Census Bureau, the township has a total area of , of which are land and , or 2.05%, are water.
As of the census