Lake Milton is a census-designated place in central Milton Township, Mahoning County, Ohio, United States. Although it is unincorporated, it has a post office, with the ZIP code of 44429. It sits on the edge of Lake Milton in northwestern Mahoning County.The community is part of the Youngstown-Warren-Boardman, OH-PA Metropolitan Statistical Area.A post office called Lake Milton has been in operation since 1942. The community takes its name from nearby Lake Milton, a reservoir impounded by a dam constructed in 1913.