Final answer:
San Antonio was considered a good location due to its defensible site advantages, such as being a peninsula and having a sheltered harbor site.
Step-by-step explanation:
San Antonio was considered a good location due to its defensible site advantages. It is located on a peninsula between the Pacific Ocean and a large bay, providing a sheltered harbor site. This allowed cannons positioned on either side of the Golden Gate to defend against enemy ships trying to pass into the San Francisco Bay. The military advantages offered by this location made it a strategic choice for the Spanish who built the fort, El Presidio Real de San Francisco, there in 1776.