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DARBY'S LINE. In mid-October 1812, William Darby, nineteenth-century geographer and man-of-letters, left Natchitoches, Louisiana, and made his way southwest in an effort to locate the elusive intersection of the Sabine River and 32°N latitude, a significant reference point first noted in the Neutral Ground Agreement of 1806. Darby's work was later used by Philadelphia map maker, John Melish, to produce his famous 1816/1818 map of Louisiana. The Adams-Onís Treaty of 1819 used Darby's Sabine/32°N intersection to define the boundary between Spanish eastern Texas and the United States. Prior to the 1837–1838 American surveys of northwestern Louisiana (and adjacent Texas), which incorporated some 6.5 miles of present-day Texas into the United States, Darby's Line served as the "customary boundary" between first Spanish, and later Mexican, Texas and the United States.

While it is not possible to precisely locate Darby's point of intersection and therefore his line north to the Red River, a comparison of landmarks present on the Darby's map and modern topographic maps indicates the line to have been located within a quarter of a mile either side of a line 5.5 miles west of the modern Texas-Louisiana boundary. See also BOUNDARIES.


Julia Kathryn Garrett, "Dr. John Sibley and the Louisiana-Texas Frontier, 1803–1814," Southwestern Historical Quarterly, 45–49 (January 1944–April 1946). J. V. Haggard, "The Neutral Ground Between Louisiana and Texas, 1806–1821," Louisiana Historical Quarterly 28 (October 1945). Jim Tiller, Before the Line. Volume I: An Annotated Atlas of International Boundaries and Republic of Texas Administrative Units Along the Sabine River-Caddo Lake Borderland, 18031841 (2010), Electronic version available at Newton Gresham Library, Sam Houston State University, Huntsville.

Jim Tiller


The following, adapted from the Chicago Manual of Style, 15th edition, is the preferred citation for this article.

Jim Tiller, "DARBY'S LINE," Handbook of Texas Online (, accessed August 01, 2015. Uploaded on February 16, 2011. Modified on September 25, 2013. Published by the Texas State Historical Association.