CLARK, John H. Texas Boundary Line: Surveyed under the Direction of the Department of Interior. Washington: 1882.
14 lithographed sheets (17 x 31 inches). Showing the boundary between Texas and New Mexico from the Rio Grande to the Red River.
By the treaty of 1819 between the United States and Spain, the boundary line established between the two countries followed the course of the Red River westward to the 100th degree of west longitude, and crossing the Red River, ran due north to the Arkansas River; all "as laid down in Melish's map of the United States", although on Melish's map of the United States the 100th meridian was erroneously shown as crossing the Red River more than one hundred miles east of this strip, and east of the fork in the River. The same line was established by the treaty of 1828 between the United States and the United Mexican States, and confirmed by the Convention of 1838 between the United States and the Republic of Texas. It became part of the boundary between the State of Texas and the adjacent territory of the United States on the admission of Texas into the Union in 1845. In 1850, however, by a legislative compact between the United States and the State of Texas, it was agreed that the northern boundary line of Texas should run west with the parallel of 36 degrees 30 minutes from its intersection with the 100th meridian.
In 1859 the eastern boundary of the panhandle of Texas which runs along the 100th meridian was surveyed and marked, under the direction of the Indian Office, by A. H. Jones and H. M. C. Brown. In 1860 Clark surveyed the northwest boundary of Texas, under the auspices of the United States and Texas Boundary Commission. For various reasons, not least the advent of the Civil War in 1861, Clark's survey was not presented until the 47th Congress, and only published in 1882 as Senate Executive Document No. 70, accompanied by these maps. However the boundary was not officially agreed upon until March of 1891. Between that date and 1912, when New Mexico became an official state and Clark's survey was once again officially recognised, the exact location of the boundary as it runs along the 103rd meridian was in dispute, partly as a result of Melish's original error.