The Neutral Ground
The Neutral Ground along the border of the United States with Spanish Texas was established as a place where neither country's military would engage. Essentially an agreement between two military leaders rather than their countries, it kept the peace but allowed a protected area for smuggling and other "criminal" activities. That mentality was part of the culture of horse smuggling in which Nicholas Trammel engage. The below is from the Texas Historical Commission. Enjoy....
November 5th, 1806 -- Border between Texas and Louisiana declared Neutral Ground
On this day in 1806, the United States and Spain signed an agreement establishing the Neutral Ground. After the Louisiana Purchase of 1803 the United States and Spain were unable to agree on the boundary between Louisiana and Texas. In 1806, in order to avert an armed clash, Gen. James Wilkinson and Lt. Col. Simón de Herrera, the American and Spanish military commanders respectively, entered into an agreement declaring the disputed territory Neutral Ground. The boundaries of the Neutral Ground were never officially described beyond a general statement that the Arroyo Hondo on the east and the Sabine River on the west were to serve as boundaries. Ownership of the strip was awarded the United States by the Adams-Onís Treaty in 1821.