TERÁN’S LINE. In the fall of 1828 Gen. Manuel de Mier y Terán, head of Mexico’s Boundary Commission, was charged by his government with locating a series of easily identifiable points along the Adams-Onís Treaty line between the Sabine and Red rivers. By late October he had established the location of the Sabine River—thirty-second parallel point of intersection called for in that treaty. Terán then moved north ultimately reaching Coates Bluff (the site of modern-day Shreveport) before returning to the Sabine.
His point of intersection on the Sabine is clearly noted on George Aldrich’s map of surveys in old Harrison County. Even though Terán apparently never actually ventured north of Cross Lake, later Mexican mapmakers would place his line on the Red River just north of Shreveport at a point far to the east of Darby’s Line. Calculations from Aldrich’s map rather precisely place his corner on the Sabine, not in the vicinity of Logansport where he actually encamped, but at a point on the river approximately six miles southeast (and downstream). A line extended north from this point passes through the western end of Cross Lake, just to the east of Mooringsport on Caddo Lake and intersects the Red River north of Mandeville, Arkansas, at a point some six miles east of the modern Texas-Louisiana line. Confirmation of the location of Terán’s Line is provided by Jehiel Brooks, later Caddo Agent for the United States, who encountered Terán in late October near the western end of Cross Lake (although Terán makes no note of such a meeting in his diary). Brooks confirmed that Terán’s line passed close to the western end of Cross Lake.
Jehiel Brooks, Summation to the Jury, ca. May 1847 in the case of Jehiel Brooks vs. Samuel Norris, District Court of Caddo Parish, Box 2, Folder 2, Item 1, Brooks-Queen Family Collection, American Catholic History Research Center and University Archives, Catholic University of America, Washington, D.C. (www.aladin.wrlc.org/gsdl/collect/brooks/brooks.shtml), accessed October 14, 2009. Manuel de Mier y Terán, Texas by Terán: The Diary Kept by General Manuel de Mier y Terán on His 1828 Inspection of Texas, Jack Jackson, ed., John Wheat, trans. (Austin: University of Texas Press, 2000). Surveys between the Sabine and Red Rivers made for titles under Radford Berry, Commissioner, Atlas Collection, Document 14, Professional Services Program Area, Surveying Division, Texas General Land Office, Austin. 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, 1803-1841 (2010), Electronic version available at Newton Gresham Library, Sam Houston State University, Huntsville.