During the interior exploration and mapping of North America, maps were created with overlapping boundaries. The Europeans and the new countries of Mexico (1821) and the United States (1775) all made conflicting claims. Maps were used to state territorial claims and establish borders. A map printed in London in this group shows a British claim as far south as present Monterey, CA. A French claim goes all the way to present Cabo San Lucas, BC Sur.

In 1773, a Franciscan priest constructed a stone monument near San Ysidero, CA. The purpose of the monument was to separate Upper and Lower California for administrative purposes. This informal point eventually became the western terminus of the US-Mexico Border south of San Diego.

The USA purchased Florida from Spain in 1819. In the early 1820’s it concluded a treaty with the newly independent Republic of Mexico. The treaty established the frontier running from the present California-Oregon border in the Northwest to the Sabine River just west of New Orleans.

Natchitoches, Louisiana (the red dot) was founded in 1714 as a French outpost on the Red River to trade with Spanishcontrolled Mexico. Two years later, Spain established a mission Nuestra Señora de Guadalupe de los Nacogdoches in what is now Nacodoches, TX (blue dot) to counter the French advance. The two towns are about forty miles apart on opposite sides of the Sabine River (green dot) As a result the Sabine became the de facto border between the Spanish province, St. Louis de Potosi and the French territory, Louisiana.

Today after almost 300 years the Sabine River is still the border between Texas and Louisiana. Both Natchitoches, LA and Nacodoches, TX are named after the Nacogdoche tribe of Caddo Indians. The Caddo had a thriving maize (corn) based culture in the Red River Valley before the arrival of the Europeans.