Final answer:
Stephen F. Austin is recognized for beginning trade with Mexico on the Santa Fe Trail in 1821 by leading 300 families into Texas under an agreement with the Mexican government.
Step-by-step explanation:
The individual credited with initiating trade with Mexico on the Santa Fe Trail in 1821 is Stephen F. Austin, who led 300 families into Texas as a part of an agreement with the Mexican government to populate the area. These families were to follow the laws of Mexico, practice Roman Catholicism, and be of good moral character. This movement of American settlers to Texas significantly increased the American population in the Mexican province, with Americans soon outnumbering the Mexican locals. The allowed settlement resulted in the foundation of what would become a vital trade route known as the Santa Fe Trail. As U.S. settlers continued to move West, trade paths like the Santa Fe Trail were crucial connections between nations for commerce.