As established in 1666, Hartford County consisted of the towns of Windsor, Wethersfield, Hartford, Farmington, and Middletown. The "Thirty Miles Island" referred to in the constituting Act was incorporated as the town of Haddam in 1668. In 1670, the town of Simsbury was established, extending Hartford County to the Massachusetts border. In the late 17th to early 18th centuries, several more towns were established and added to Hartford County: Waterbury in 1686 (transferred to New Haven County in 1728), Windham in 1694 (transferred to Windham County in 1726), Hebron in 1708 (transferred to Tolland County in 1785), Coventry in 1712 (transferred to Windham County in 1726), and Litchfield in 1722 (transferred to Litchfield County in 1751).