Simón de Herrera was born at Santa Cruz de Tenerife, in the Canary Islands, in 1754. He joined the Guimar Militia as sublieutenant on September 12, 1763, and was promoted to captain of militia on August 2, 1769. He transferred to the Zamora Infantry Regiment with the rank of sublieutenant on August 4, 1775. He was promoted through the ranks to lieutenant colonel in 1795. He served in the government of Colotlán, west of Aguascalientes, Mexico, and as commandant of the militia of New Galicia. He formed the Provincial Regiment of Guadalajara with battalions from Tepic, Bolaños, and several frontier companies and commanded it from February 9, 1788, until June 21, 1794. He was then promoted to the government of the province of Nuevo León, where he served as captain of the Lancer Company of Punta de Lampasas and commander of the provincial militia. Among his military actions was an expedition to South America in 1776 and the siege and capture of Portuguese colonies on the island of Santa Catalina, Puntagrosa, Santa Cruz, Ratones, and the fortified port of Feligrecia de San Antonio. He participated in the siege of Montevideo before returning to Spain to join in the blockade of Gibraltar until November 10, 1781. He returned to America with the Army of Operations and fought under the command of Bernardo de Gálvez at Guarico from February 10, 1782, until July 23, 1783. He then served as special courier of dispatches to Spain and France. After returning to Mexico, he formed a plan of the missions of Nayarit and Galicia, and by 1797 was ready to lead his provincial militia against 200 marauding Apaches and Comanches, an expedition that was singularly successful. He married an English lady at Cádiz and was well acquainted with George Washington and the intricate government of the United States. He was accused, along with his brother Pedro, who was left in command at Monterrey when Simón went to Texas, of extorting money from ranchers in lieu of their serving on the frontier.
For more than seven years Herrera defended Spanish Texas against domestic and foreign enemies. He was a lieutenant colonel and governor of Nuevo León when Nemecio Salcedo y Salcedo, commandant general of the Provincias Internas, became alarmed about American intentions and ordered him to protect East Texas. When Herrera arrived at San Antonio on May 31, 1806, he was made commandant of the Louisiana frontier. Supported by more than 600 troops, he patrolled the area between the Sabine and the Arroyo Hondo, occupied Bayou Pierre, and defied Gen. James Wilkinson until Salcedo ordered him to fall back. In November 1806 Herrera and Wilkinson entered into the Neutral Ground agreement, which was observed by Spain and the United States until 1819, when the Adams-Onís Treaty was made.
After this agreement Herrera devoted his efforts to improving the defenses of Texas. Loyal to the Royalists during the revolt led by Miguel Hidalgo y Costilla, Herrera was imprisoned in January 1811, during the Casas Revolt in San Antonio. Herrera and Governor Manuel María de Salcedo were sent to Santa Rosa, Coahuila, for detention on Ignacio Elizondo's hacienda. The two prisoners persuaded Elizondo to desert the patriot cause. Shortly after his desertion, Elizondo ambushed Hidalgo and other leaders on their way to Texas, thus preventing San Antonio's becoming the center of the rebellion in New Spain. In July 1811 Herrera returned to San Antonio as ad interim governor, a post he held until Salcedo reluctantly resumed the position in December. Almost at once, Salcedo and Herrera were confronted with the Gutiérrez-Magee expedition, an enterprise that captured Nacogdoches and La Bahía by November 1812. Herrera and Salcedo immediately laid siege to La Bahía; but, after failing to dislodge the filibusters, they withdrew toward San Antonio in February and on March 29 suffered a disastrous defeat in the battle of Rosillo. San Antonio surrendered unconditionally on April 1, and two days later Mexicans among the filibusters murdered Herrera, Salcedo, and several other Spaniards. After Joaquín de Arredondo's defeat of the filibusters at the battle of Medina, the remains were recovered for Christian burial in San Antonio.