Marlboro is a town in Windham County, Vermont, United States. The population was 1,722 at the 2020 census. The town is home to both the Southern Vermont Natural History Museum and Potash Hill, the campus that was formerly Marlboro College. Potash Hill hosts the Marlboro Music School and Festival each summer, as well as other arts and educatio…Marlboro is a town in Windham County, Vermont, United States. The population was 1,722 at the 2020 census. The town is home to both the Southern Vermont Natural History Museum and Potash Hill, the campus that was formerly Marlboro College. Potash Hill hosts the Marlboro Music School and Festival each summer, as well as other arts and education programs throughout the year.