Final answer:
The first permanent Spanish settlement in Texas was St. Augustine, but the first legal American settlement under Mexican jurisdiction was established by Stephen F. Austin in 1821 after Mexico's independence from Spain.
Step-by-step explanation:
The Spanish settlers formed their first permanent community in what is now Texas at San Agustín (St. Augustine). This was significantly south of the later American incursion into Mexican territory. However, the first legal settlement of American settlers in Texas under the jurisdiction of Mexico was led by Stephen F. Austin in 1821, who brought the first 300 families into the region as part of an agreement with the new Mexican government after Mexico gained independence from Spain that same year. These settlements were part of an empresario system, where individuals such as Moses Austin and later his son Stephen were granted the right to bring settlers to Texas in exchange for land, with the aim of increasing the non-Native population and providing security against Native American tribes and potential American expansion.