Final answer:
Stephen F. Austin is recognized for establishing the first legal American settlement in Texas in 1822, leading 300 families into the region. His actions set the stage for the significant growth of American population in Texas and prompted events leading to the Texas Revolution and the formation of the Republic of Texas.
Step-by-step explanation:
The person who established the first legal American settlement in Texas in 1822 was Stephen F. Austin. He led 300 families into the Mexican province of Texas under an invitation from AgustÃn I, emperor of Mexico. Austin carried out his father's plans after his death in 1821, taking advantage of the colonization laws Mexico had passed to encourage immigration.
Despite initial conditions that settlers must be of good moral character, abide by Mexican laws, and be Roman Catholic, the number of American settlers exploded by the year 1827, reaching a population of 12,000, due to the favorable conditions such as the offer of land at generous terms and the ability to pay in installments.
This influx of settlers led to cultural and political tensions which contributed to events such as the Texas Revolution and eventually the formation of the independent Republic of Texas, also known as the Lone Star Republic. Stephen F. Austin is often referred to as the "Father of Texas" for his role in leading the first American settlers to the region and establishing a foothold that would eventually lead Texas to become a part of the United States.