High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! Springfield Township is one of twenty townships in Allen County, Indiana. As of the 2000 census, its population was 3,697. The principal town in Springfield Township is the village of Harlan. Springfield Township covers an area of 35.42 square miles; 0.07 square miles (0.2 percent) of this is water. Allen County is the largest county (by area) in the state of Indiana, United States.