José Manuel Rafael Simeón de Mier y Terán, Mexican general, was born in Mexico City on February 18, 1789, the eldest of three sons of Manuel de Mier y Terán and María Ignacia de Teruel y Llanos. In February 1824 he married Josefa Velasco de Teruel. He visited Texas twice: first, as leader of a boundary-commission expedition to Nacogdoches in 1828–29; and second, as commandant general of the Eastern Interior Provinces (see PROVINCIAS INTERNAS), in which role he visited Galveston Bay in November 1831. Mier, who showed special aptitude for mathematics and engineering, graduated from the College of Mines in Mexico City in 1811. He joined José María Morelos in the movement for Mexican independence in 1811 and fought under Ignacio Rayón. In 1821 he joined future emperor Agustín de Iturbide to expel the Spaniards under the Plan de Iguala. He served in the first constituent congress in 1822 as a member of the committee on colonization of unoccupied lands. He was made a brigadier general in 1824 and served nine months as minister of war. In 1827 President Guadalupe Victoria named him to lead a scientific and boundary expedition into Texas to observe the natural resources and the Indians, to discover the number and attitudes of the Americans living there, and to determine the United States-Mexico boundary between the Sabine and the Red rivers.
The Comisión de Límites (Boundary Commission) left Mexico City on November 10, 1827, and reached San Antonio on March 1, 1828, San Felipe on April 27, and Nacogdoches on June 3. Mier y Terán traveled with a military escort in a huge coach inlaid with silver along with Rafael Chovell, a mineralogist and later military commander at Lavaca; Jean Louis Berlandier, a botanist, zoologist, and artist; and José María Sánchez y Tapía , cartographer and artist. All kept diaries that have been published in part. Illness and muddy roads delayed the commission, and the general remained in East Texas until January 16, 1829, when he started for Mexico City. In his report on the commission, Mier y Terán recommended that strong measures be taken to stop the United States from acquiring Texas. He suggested additional garrisons surrounding the settlements, closer trade ties with Mexico, and the encouragement of more Mexican and European settlers. His suggestions were incorporated into the Law of April 6, 1830, which also called for the prohibition of slavery and closed the borders of Texas to Americans.
After the completion of his reports, Mier y Terán was ordered to Tampico to help repulse a Spanish invasion in August 1829. He was made second in command under Antonio López de Santa Anna, and the pair became heroes of the nation by their successful expulsion of the Spanish force on August 20. Early in 1830 President Anastasio Bustamante named Mier y Terán commandant general of the Eastern Interior Provinces, a position in which he supervised both political and military affairs in Texas, Coahuila, Nuevo León, and Tamaulipas. His headquarters were near the new port of Matamoros, which had just opened. The general visited Anahuac from November 9 to 24, 1831, to install George Fisher as collector of customs there. Displeased by the attitudes of the Texans who refused to pay taxes, the general ordered Fisher to enforce collection of the national tariff on the Brazos River, even though the deputy for that post had not arrived. He also ordered John Davis Bradburn to enforce national laws regarding titles and to disband an ayuntamiento recently installed without government authorization at Liberty. These orders caused friction with the settlers, who blamed Fisher and Bradburn for acting as despots (see ANAHUAC DISTURBANCES). During his tenure as comandant general, Mier y Terán supported constituted authority whether of a Federalist or Centralist regime and continued to be concerned over the inability of incoming American settlers to assimilate into the Mexican culture. When Santa Anna pronounced against the Centralist administration in January 1832, Mier y Terán tried to defend the Eastern Internal Provinces from the Federalist rebels. In poor health and subject to depression, he grew despondent over the problems of colonization in Texas and the continuing political problems on both the state and national levels. On July 3, 1832, with the federalist forces gaining a significant victory near Matamoros and the increasing influx of Anglo-American settlers after abrogation of the Law of 1830, the general committed suicide by falling on his sword behind the church of San Antonio in Padilla, Tamaulipas. It was the same place where Emperor Iturbide had been shot after his return from exile. Mier was buried in the tomb with the former emperor until 1938, when Iturbide's remains were removed to Mexico City.