Many Mexicans suddenly became Mexican-American when the border moved in the aftermath of the U.S.-Mexican War. One historic site that was instrumental in that process is the Resaca de la Palma Battlefield, part of Palo Alto Battlefield National Historical Park in Brownsville, TX.

Resaca de la Palma was one of a series of battles fought in the Rio Grande delta in the spring of 1846. In March of that year, a U.S. Army, commanded by General Zachary Taylor, marched into the region and established a fort on the banks of the Rio Grande. Taylor raised the Stars and Stripes over his post to claim the river as the southern boundary of the newly-annexed state of Texas.

Mexico resisted this move. Texas had declared its independence from Mexico in 1836 and defeated the army of Antonio López de Santa Anna in battle, but Mexican leaders had never surrendered hopes of reclaiming the territory. They denounced the U.S. annexation of the Republic of Texas in 1845 as an act of aggression. They became even more frustrated when U.S. President James Polk claimed the Rio Grande as the boundary of Texas. Mexico had always placed the boundary of Texas along the Nueces River, far to the north, and believed that Polk was attempting to seize additional territory. When U.S. troops mobilized on the north bank of the river, Mexican troops gathered on the south bank, in the city of Matamoros.

After losing the battle at the Rio Grande in 1846, General Mariano Arista turned to politics. He served Mexico as president between 1851 and 1853.. Public Domain

Fighting soon followed. In April of 1846, Mexican General Mariano Arista sent troops across the river to force the U.S. Army from the disputed land. On April 25, those troops defeated a small U.S. scout party in what would become the opening clash of a two-year war. The Mexican troops continued their march and attempted to surround the U.S. fort on the river and force the occupants into submission.

They were unable to trap the U.S. force. Before the Mexicans could move into position, General Taylor marched his troops to the Gulf coast, about 20 miles away, to meet ships carrying the supplies needed to withstand a siege. When Arista’s troops began their bombardment of the post—informally called Fort Texas—only a small detachment of U.S. troops remained within.

On May 7, General Taylor marched with 2,300 troops to relieve the siege of his fort. Arista, with a force of about 3200 troops, attempted to halt his advance. On May 8, on the broad coastal prairie at Palo Alto, he engaged the U.S. troops in a six hour long artillery battle. The fight went badly for the Mexicans as the superior U.S. cannons pounded their lines and caused hundreds of casualties. When nightfall brought the battle to a close, General Arista decided to fall back and seek a position where the enemy guns would cause less damage.

He selected Resaca de la Palma, a brush covered ravine about 5 miles to the south. Placing his troops in the dense thickets, he believed that he could make a strong defensive stand. But when the U.S. Army reached this point on the afternoon of May 9, he could not hold the ground. His soldiers, who had fought valiantly the previous day, had become demoralized by the carnage in their ranks. When the U.S. troops engaged them in hand-to-hand combat, the dispirited Mexican force broke and fled. By nightfall, they had retreated back across the Rio Grande.

The battle occurred just a day before news of the initial skirmish reached Washington D.C. Upon learning that Mexican troops had crossed the Rio Grande and attacked U.S. troops, President Polk announced that Mexico had invaded U.S. territory and “shed American blood upon the American soil.” Within days, on May 13, the U.S. declared war.

Mexican troops remained convinced that it was the U.S. Army that had invaded Mexican soil, but the defeat at Resaca de la Palma prevented them from pressing their claims. The broken Mexican army could not generate another push across the Rio Grande. They also could not hold Matamoros and, on May 18, abandoned the city of Matamoros to a U.S. occupation.

For one night each year, 8,000 candles are lit on the field at Resaca de la Palma Battlefield in remembrance of the shared heritage between the people living at the Mexican-American border. Courtesy of John Scheiber

The war that started at Palo Alto and Resaca de la Palma continued for almost two years, and drew to a close only after U.S. troops occupied the Mexican capital. Only then did Mexican officials begin to negotiate a settlement that would include recognition of the Rio Grande as the international boundary and sale of additional territories extending to the Pacific Coast. The treaty that was signed on February 2, 1848 also dictated that Mexicans occupying those lands would gain rights as U.S. citizens.

That process had already started before the war ended. Following the clash at Resaca de la Palma, Mexican residents living north of the Rio Grande realized that the United States was unlikely to lose its hold on the land. Some fled to Mexico, while others stayed with their homes and property to become citizens of the United States.

Today the Resaca de la Palma Battlefield lies in the center of Brownsville, Texas, a community with many descendants of these Mexican-Americans. Much of the area of dense brush has been replaced by streets, homes, and businesses, but a 34 acre portion of this important battlefield remains. In August 2011, Palo Alto Battlefield National Historical Park acquired this property as a second unit of the park. The park currently opens the site for special events, like the annual Memorial Illumination, a ceremonial lighting of 8,000 candles to honor each of the U.S. and Mexican soldiers who fought in the Palo Alto/Resaca battles. In time, the public will have even greater access to trails, interpretative media, and programs on the site.