Decatur Township is the smallest in geographic size and in population of the nine
townships in
Marion County,
Indiana,
United States. As of the
2010 census, it had a population of 32,388. Located on the southwest corner of the county, the township is home to the new
Indianapolis International Airport main terminal. The city of
Indianapolis and Marion County are a merged unit. Long one of the most rural sections of the county, Decatur Township has seen many new residential and commercial developments. AmeriPlex, one of the largest industrial parks in Indiana, is in Decatur Township. Through the
White River, Decatur and Perry townships share the only water boundary among Marion County's townships.