Windham County was created from Hartford and New London counties by an act of the Connecticut General Court on May 12, 1726. In 1749, the county gained Woodstock from Worcester County, Mass., but the following towns, which were originally part of Windham County, were transferred to other counties: Union (in 1785), Coventry (in 1786), Lebanon (in 1824), Columbia (in 1827), Mansfield (in 1827), and Voluntown (in 1881).