Milaca is a city and the county seat of Mille Lacs County, Minnesota. The population was 3,021 at the time of the 2020 census. It is situated on …Milaca is a city and the county seat of Mille Lacs County, Minnesota. The population was 3,021 at the time of the 2020 census. It is situated on the Rum River. A post office has been in operation at Milaca since 1883. The name Milaca is derived from shortening and alteration of Mille Lacs Lake.