 The boundary between Kentucky and Tennessee was defined as 36°30′, based on the Royal Colonial Boundary of 1665 that set the boundary of the Colony of Virginia and the Province of Carolina.In 1779 and 1780, surveyors were sent to mark the line on the ground as far as the Tennessee River.As they worked west their line drifted north until by the time they reached the river they were about 10′ north of 36°30′.