Royal Colonial Boundary of 1665
The Royal Colonial Boundary of 1665 marked the border between the Colony of Virginia and the Province of Carolina from the Atlantic Ocean westward across North America. The line follows the parallel 36°30′ north latitude that later became a boundary for several U.S. states as far west as the Oklahoma Panhandle, and also came to be associated with the Missouri Compromise of 1820.
It was a brainchild of King Charles II of England, and was intended to stretch from the Atlantic to the Pacific Ocean. By 1819 it was surveyed as far west as the Mississippi River near New Madrid, Missouri.
The boundary Charles II envisioned was one of the most grandiose in history. To decree an imaginary geographic straight line, 3,000 miles long, as a boundary across an unknown continent that he didn't even own was the height of royal pomposity.
The survey was done in five stages, using cadastral and geodetic surveying, being one of the first attempts to mark a boundary so long that it had to be concerned with the curvature of the Earth. A major aberration in the line occurs south of Damascus, Virginia due to the surveyor, Peter Jefferson (father of Thomas Jefferson), continually edging north of the proper latitude. There are three theories about this:
- The surveyor was drunk.
- Iron deposits in the mountains interfered with compass readings.
- People who lived in Tennessee exerted influence over the location of the line. (There were few British subjects living in Tennessee at the time Peter Jefferson and his partners marked their segment from the Dan River to what is now the Tennessee/North Carolina state line.)
The line was extended in 1779 and 1780 to the point at which it would first cross the Cumberland River. From there, the state of Virginia hired Thomas Walker to survey the line to the Mississippi River. Walker did not do a perfect job due to dense virgin forest, mountainous terrain, and rough riverbeds. In 1821 the state of Tennessee did a survey of the line to determine its true border with Kentucky, but this was not resolved since Kentucky was not participating. A joint survey by the two states was conducted in 1859, commanded by Austin P. Cox and Benjamin Pebbles. They started a 320-mile survey from the New Madrid Bend of the Mississippi River to the Cumberland Gap, placing a 3-foot-high stone slab every five miles.
The line would later be used for approximating a de facto boundary north of which slavery could not be practiced, as established in the Missouri Compromise of 1820.  A marker at the Cumberland Gap National Historical Park denotes where the boundaries of Kentucky, Tennessee, and Virginia intersect. Under the Royal Proclamation of 1763 it also marks how far west a British American colonist was allowed to reside. Its exact location is N 36'36.045, W 83'40.518.
- "Royal Colonial Boundary of 1665". American Society of Civil Engineers. Archived from the original on 2012-07-02. Retrieved 2008-03-22.
- A Brief History of Washington County, Virginia, Washington County, Virginia website (accessed 22 March 2008)
- Kleber, John E. The Kentucky Encyclopedia. (University Press of Kentucky). pp. 102–103.
- In 1859, slavery existed north of the Tennessee/Kentucky border. Kentucky was a slave state that stayed in the Union and did not abolish slavery until the 13th Amendment was adopted. The Missouri Compromise line, as a border between slave and free territory, existed only west of the Mississippi River in the territorial land acquired in the Louisiana Purchase. East of the Mississippi River, slavery was prohibited north of the Ohio River by the 1787 law creating the Northwest Territory.
- "Cumberland Gap". Tennessee History for Kids, Inc. Retrieved 2008-03-22.
- "International GPS waypoint registry (Kentucky)". FAR laboratories.