Westmoreland County, Connecticut was a county established by the State of Connecticut in October 1776, encompassing the present-day area of Wyoming Valley, in northeastern Pennsylvania. Both colonies claimed this territory and the issue was further confused by the Six Nations selling the territory to both Connecticut in 1754 and again to Pennsylvania in 1768. The first of the Yankee-Pennamite Wars were fought in and around the County, from 1771 through 1775.^[1]

In December 1782 a court of arbitration appointed by the Continental Congress met in Trenton, New Jersey, and made a unanimous decision in favor of Pennsylvania's claim. In compensation, Connecticut received equivalent territory of 3,300,000 acres named the Western Reserve, in the future northeast of Ohio. Pennsylvania then refused to confirm the private land titles of the settlers, which caused the Second of the Yankee-Pennamite Wars. It briefly seceded to become the short-lived State of Westmoreland in 1784. Connecticut finally ceded it to Pennsylvania in 1786 after Pennsylvania confirmed the land titles and Westmoreland County was renamed to Luzerne County.^[1]

It has no relationship to the current Westmoreland County, Pennsylvania, which is located on the western and opposite side of the state.