Ackley, Iowa. Homefacts City Report. Ackley is located in Hardin County, IA. The population is 1,469, making Ackley the 3rd largest city in Hardin County. There are 3 public schools in Ackley with an average Homefacts rating of B+. The total crime rate for Ackley is low, and there are 6 registered sex offenders residing in the city.