In 1777, Bernardo de Galvez, Governor of Spanish Louisiana, began to have a considerable impact on the ranchos in the area between San Antonio and the La Bahia Mission settlement.

A supporter of the cause of American Independence, Galvez made a request to Domingo Cabello y Robles, the Governor of Spanish Texas, for cattle to feed the troops in Louisiana. It is estimated that between 1779 and 1782, around 15 to 20 thousand head of cattle per year were herded out by area ranchers. Santiago Seguin was one such provider of cattle and represents the many Spanish landowners in Texas who aided the cause of the American Revolution.

Seguin was active in the often turbulent affairs of the Presidio of San Antonio de Bexar. In 1783, the ranchers experienced a very bad season and Seguin was a signer in a petition, “The San Fernando Memorial,” for damages brought against the previous Governor of Texas. By 1786, Seguin is listed as the region’s eighth largest cattle exporter. In 1786, he co-signed a note to guarantee the tithes given to the Catholic Church. In January 1787, a round-up of cattle and horses was initiated, and Seguin was one of the signatories to that agreement. At the time he was also a Regidor or Councilman of the Presidio of San Antonio de Bexar.

His wife, Maria Guadalupe Fuentes, died in 1792. Seguin died sometime after August 17, 1796. His descendants would continue to prosper. His grandson, Juan N. Seguin, would become an important figure in the Texas Revolution of 1836. Santiago Seguin’s name is engraved on the Texas Society DAR Patriot Monument in the Texas State Cemetery, Austin, Texas.