The parallel 36°30′ north is a circle of latitude that is 36 and one-half degrees north of the equator of the Earth. This parallel of latitude is particularly significant in the history of the United States as the line of the Missouri Compromise, which was used to divide the prospective slave and free states west of the Mississippi River, with the exception of Missouri, which is mostly north of this parallel. In the United States In the United States, the parallel 36°30′ forms part of the boundary between Tennessee and Kentucky, in the region west of the Tennessee River and east of the Mississippi River. This parallel also forms part of the boundary between Missouri and Arkansas in the region west of the St. Francis River, and part of the boundary between the Oklahoma Panhandle and the Texas Panhandle. The rest of the boundaries between Virginia and North Carolina; between Virginia and Tennessee; and between Tennessee and Kentucky lie close to the parallel 36°30′. 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′. Despite this error the boundary was set along the line surveyed. The final part of the Kentucky-Tennessee boundary, between the Tennessee River and the Mississippi River, was not surveyed until after 1819 when treaties extinguished Native American claims in the area. The final portion was surveyed east from the Mississippi River along 36°30′. Due to the relative precision of the survey of 36°30′ on the Mississippi River, Congress decided to continue the line west as the northern boundary of Arkansas Territory, with the exception of the Missouri Bootheel. The parallel 36°30′ north is part of a nearly straight east-west line of state borders (with small variations) starting on the East Coast of the United States, beginning with the border between Virginia and North Carolina. However, this boundary and the one between Kentucky and Tennessee line lies a few miles north of 36°30′ in places. The line west of Arkansas is slightly further north at 37°. In southeastern Missouri, the Missouri Bootheel