Simón de Arocha was the eldest of fifteen children of Francisco and Juana (Curbelo) de Arocha, both Canary Islanders in Texas. He was born in San Antonio de Béxar seven months after the isleños arrived there. In 1752 he married María Ignacia de Urrutia; their union produced eight children. Like his father, who had served as city clerk and public notary, Simón held important administrative posts. He was a judge over distribution of public lands and later an alcalde. He also served as commander of the provincial militia, in which he was a lieutenant general. In this capacity he escorted the uprooted Adaesaños (see LOS ADAES) to the new Trinity River site of Bucareli in 1774. When Teodoro de Croix visited Texas in 1778, Arocha prepared a census report of the province for the new commandant general and his historian, Fray Juan Agustín Morfi.
Simón and his brother Juan obtained title to eight leagues of land north of the site of present Floresville in 1782. With this ranch, called San Rafael de Pataguilla, they and their kinsmen soon became leading cattlemen of the province. Simón was instrumental in forging a roundup agreement with the missions in 1787. Three years later he and other family members virtually controlled the local governing body, the cabildo. When they attempted to use their influence to obtain another ranch at the junction of the Guadalupe and San Marcos rivers, other stockmen lodged a vigorous protest and were supported by Governor Rafael Martínez Pacheco. The ensuing feud cost the governor his job. Don Simón died on July 29, 1796; his wife, on April 27, 1812.
During the revolutionary disturbances of the early nineteenth century, in which the Arochas were dedicated insurgents, most of their property was confiscated. With the coming of Mexican independence, however, Arocha's grandson José Ignacio managed to confirm title to the original Arocha grant.