3,500 Americans Assemble On The Nueces River

The United States supported Texas when it claimed all land north of the Rio Grande, and this provoked a dispute with Mexico.

In June 1845, James K. Polk sent General Zachary Taylor to Texas, and by October, 3,500 Americans were on the Nueces River, prepared to defend Texas from a Mexican invasion. Polk wanted to protect the border and also coveted the continent clear to the Pacific Ocean. Polk had instructed the Pacific naval squadron to seize the California ports in case Mexico declared war. At the same time he wrote to Thomas Larkin, the American consul in Monterey, that a peaceful takeover of California would be welcomed.

One of the first settlers to scout the area was Cpt. Blas María de la Garza Falcón in 1766. From before the end of the Texas Revolution, Mexico recognized that the Nueces River was historically the border of Texas from the rest of the country. However, the Republic of Texas claimed the Rio Grande as its border with Mexico, citing the Treaty of Velasco signed by Mexican President Santa Anna who agreed to the Rio Grande border after losing the Battle of San Jacinto. This dispute continued after the annexation of Texas, and was one of the causes of the Mexican-American War. The Treaty of Guadalupe Hidalgo ended the dispute, with Mexico recognizing the Rio Grande as its northern border.
On August 10, 1862 Pro-Union Germans from the Texas Hill Country trying to flee to Mexico were ambushed and killed by Confederates—the Nueces massacre.