Sidney is a town in Kennebec County, Maine, United States. The population was 4,645 at the 2020 census. Sidney was incorporated as a town on January 30, 1792. The town was named for Sir Philip Sidney, an English author. Sidney is included in the Augusta, Maine micropolitan New England City and Town Area. Since 1937, the town has been the ho…Sidney is a town in Kennebec County, Maine, United States. The population was 4,645 at the 2020 census. Sidney was incorporated as a town on January 30, 1792. The town was named for Sir Philip Sidney, an English author. Sidney is included in the Augusta, Maine micropolitan New England City and Town Area. Since 1937, the town has been the home of the New England Music Camp.