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.

It is a historic civil engineering landmark, as designated by the American Society of Civil Engineers. It would later to be said of the project:

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:

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