Jacob Brown, United States Army officer, was born in Massachusetts and enlisted as a private in the Eleventh United States Infantry on August 3, 1812. By the time of his commissioning as an ensign in the Eleventh Infantry on April 15, 1814, he had risen to the rank of sergeant. Promotion to third lieutenant came on May 1 and to second lieutenant on September 1, 1814. On May 17, 1815, he was transferred to the Sixth Infantry, where he served as regimental quartermaster from April 16 to June 1, 1821. He was promoted to first lieutenant on August 18, 1819, to captain on April 7, 1825, and to major on February 27, 1843.
With the outbreak of the Mexican War Brown and his regiment were ordered to the Rio Grande with Gen. Zachary Taylor's army of occupation. When Mexican general Mariano Arista's army crossed the Rio Grande on April 1, 1846, Taylor ordered the strengthening of Fort Texas, on the north bank opposite Matamoros. By May 1 the fortification was complete, and Taylor marched the bulk of his army toward Point Isabel to protect his supply line, leaving Brown in command of Fort Texas. Brown's garrison consisted of elements of the Seventh Infantry, Capt. Allen Lowd's four eighteen-pounder cannons, and Capt. Braxton Bragg's battery of field artillery, about 500 men in all. At 5:00 a.m. on May 3, Arista began his attack on Fort Texas with a bombardment from Matamoros and investment by Gen. Pedro Ampudia's infantry brigade. Lowd's eighteen-pounders quickly silenced the Mexican artillery, but a second battery downriver and out of range of the lighter American guns soon took up the bombardment. Hearing the sound of the guns, Taylor dispatched Texas Ranger Samuel H. Walker with instructions to Brown to defend Fort Texas to the last man. Although he outnumbered Brown's garrison by several thousand men, Ampudia determined that his artillery could not breach the fort's dirt walls and that an assault would be too costly and so settled into a formal siege. He posted Gen. Antonio Canales's irregular cavalry on the road to Point Isabel to block American reinforcements and supplies, then continued his bombardment and waited for starvation to compel Brown's surrender. At about 10:00 a.m. on May 6, 1846, Brown was mortally wounded by an enemy shell; he died on May 9. Command of the fort devolved upon Capt. Edgar S. Hawkins, who refused Ampudia's surrender demand on the afternoon of the sixth and held his lines until Arista withdrew Ampudia's command beyond the Rio Grande on May 8. Major Brown was one of the only two American fatalities in the siege. Fort Texas was renamed Fort Brown in his honor, and the city of Brownsville derived its name from that of the fort.