Allin Township is located in McLean County, Illinois. As of the 2010 census, its population was 919 and it contained 389 housing units. Allin Township was originally named Mosquito Grove Township, but changed its name on March 4, 1867.
According to the 2010 census, the township has a total area of 36.25 square miles (93.9 km2), all land.
Coordinates: 40°26′20″N 89°12′31″W / 40.43889°N 89.20861°W / 40.43889; -89.20861