Milton is a city in Rock County, Wisconsin, United States. The population was 5,716 at the 2020 census. The city was formed as a result of th…Milton is a city in Rock County, Wisconsin, United States. The population was 5,716 at the 2020 census. The city was formed as a result of the 1967 merger of the villages of Milton and Milton Junction. In November of that year, ballots were cast by 1,093 voters from both villages, and the referendum to merge the two was approved by 77%.