The American Civil War Battle of Palmito Ranch was fought on May 12 – May 13, 1865, and in the kaleidoscope of events following the surrender of Robert E. Lee's army, was nearly ignored. It was the last major clash of arms in the war.

Early in 1865, both sides in Texas agreed to a gentlemen's agreement that there was no point to further hostilities. Why the needless battle even happened remains something of a mystery—perhaps Union Colonel Theodore H. Barrett had political aspirations (he certainly had little military experience). Barrett instructed Lieutenant Colonel David Branson to attack the rebel encampment at Brazos Santiago Depot near Fort Brown outside Brownsville.

By that time, most Union troops had pulled out from Texas for campaigns in the east. The Confederates were concerned to protect what ports they had for cotton sales to Europe, as well as importation of supplies. Mexicans tended to side with the Confederates due to a lucrative smuggling trade.

Union forces marched upriver from Brazos Santiago to attack the Confederate encampment, and were at first successful but were then driven back by a relief force. The next day, the Union attacked again, again to initial success and later failure. Ultimately, the Union retreated to the coast.

There were 118 Union casualties. Confederate casualites were "a few dozen" wounded, none killed. Nothing was really gained on either side; like the war's first big battle (First Bull Run to the Union, First Manassas to the Confederates), it is recorded as a Confederate victory. Texas armies formally surrendered on May 26, 1865; Confederate general Kirby Smith surrendered his forces in the Trans-Mississippi Department on June 2nd.

It is worth noting that private John J. Williams of the 34th Indiana Volunteer Infantry was the last man killed at the Battle at Palmito Ranch, and probably the last of the war. Fighting were white, African, Hispanic and native troops. Reports of shots from the Mexican side are unverified, though many witnesses reported firing from the Mexican shore.