North Liberty is a city in Johnson County, Iowa, United States. It is a suburb of Iowa City and part of the Iowa City Metropolitan Statistical Area.As of a special census in 2015, the city population was 18,299. From 2000 to 2010, North Liberty was the second fastest-growing city in Iowa. A 2017 LendEDU poll named North Liberty the 9th most educated city in the United States and the most educated city in the Midwest.