Marengo is an unincorporated census-designated place located in the town of White River, Ashland County, Wisconsin, United States. Marengo is located on Wisconsin Highway 13 10 miles northwest of Mellen. Marengo had a post office, which closed on June 27, 2009. At the 2020 census, its population was 148, up from 111 at the 2010 census. Bus service to the community is provided by Bay Area Rural Transit.