On April 25, 1846, at an abandoned hacienda somewhere near this site, Captain Seth Thornton and less than 70 U.S. dragoons were ambushed by some 2,000 Mexican troops commanded by General Anastasio Torrejon. During the skirmish, 16 American soldiers were killed. The remainder, including Thornton, were captured and taken to Matamoros. After President Polk received news of the incident, he addressed a joint session of Congress, announcing: “American blood has been shed on American soil.” On May 13, 1846 Congress declared war on Mexico. The marker erroneously refers to the leader of the dragoons as Captain “Phillip” Thornton.