From Ancestry.com Wiki
Sidney is a town in Kennebec county, Maine. It was formed in 1792. Sidney began keeping vital records in 1772 and town records in 1700*. For more information, contact the county at 2986 Middle Rd., Sidney 04330. On the attached map, Sidney is shown as 13 in Kennebec county.
For information about the state of Maine see Maine Family History Research.