From the Annals of the Border – In 1819, U.S. Secretary of State John Quincy Adams and Spanish foreign minister Luis de Onis y Gonzalez-Vara signed the Adams-Onis Treaty also known as the Florida Treaty. Spain ceded Florida to the U.S. in exchange for settling the long simmering boundary dispute between the U.S. and New Spain. Spain was frankly interested in jettisoning Florida as it was already overwhelmed with wars for independence in South America and periodic upheaval what was soon to be Mexico. The treaty set the U.S./New Spain boundary at the Sabine River and on through the great plains and Rocky Mountains following the Red River and Arkansas River – basically according to the terms of the Louisiana Purchase – and then on west to the Pacific Ocean along the 42nd Parallel. The U.S. renounced any claims to Texas and agreed to pay residents’ claims against the Spanish government up to a total of $5,000,000. The treaty was short-lived as Mexico was granted independence from Spain in 1821. Mexico ratified the boundaries of AO Treaty by agreeing to the Treaty of Limits in 1828. The boundary stood until the Texas Revolution and the later the Mexican-American War.
From the Annals of Broken Promises – In 1819 the Adams-Onís Treaty was signed by Secretary of State John Quincy Adams for the United States and Luís de Onís for Spain. The treaty fixed the western boundary of the Louisiana Purchase and had the effect of renouncing U.S. claims to Texas. The newly fixed boundary began at the mouth of the Sabine River and ran along its south and west bank to the thirty-second parallel and thence directly north to the Río Roxo (Red River). The boundary then followed the course of the Río Roxo westward to the 100th meridian and then due north to the Arkansas River. From there the boundary followed the southern bank of the Arkansas to its source near the 42nd parallel and then following the 42nd to the “South Sea” (Pacific Ocean). Spain delayed ratification of the treaty and in the interval Mexico declared its independence. The newly formed country refused to accede to the terms of the treaty and never recognized the negotiated boundary.
From the Annals of Neutrality – In 1806, the United States and Spain established the “Neutral Ground” between Louisiana and Texas. After the Louisiana Purchase, the US and Spain had been unable to agree on the boundary between Louisiana and Texas despite Spain having once controlled the area. To avoid an armed clash over the disputed land, Gen. James Wilkinson and Lt. Col. Simón de Herrera, the American and Spanish military commanders, entered into an agreement establishing a Neutral Ground between Texas and Louisiana. Even the boundaries of the NG were never exactly prescribed. The NG was generally described as being bordered by the Arroyo Hondo on the east and the Sabine River on the west. The Gulf of Mexico clearly constituted the Southern boundary and most likely the thirty-second parallel of latitude formed the northern boundary. Despite an agreement that no settlers would be permitted in the NG, settlers from both Spanish and American territory moved in. Predictably, the NG became fertile ground for illegal activity and the US and Spain cooperated in sending joint military expeditions in 1810 and 1812 to enforce order and expel undesirables. The US obtained ownership of the NG with the signing of the Adams-Onis Treaty in 1821.