Final answer:
St. Augustine was the Spanish settlement founded by Pedro Menéndez de Avilés before other prominent English settlements. It became the oldest continuously-settled European settlement in the continental United States, serving to reduce the threat of French privateers and strengthen Spain's claim to the area.
Step-by-step explanation:
The Spanish settlement established by Pedro Menéndez de Avilés, well before Roanoke, Jamestown, or Plymouth, is St. Augustine. St. Augustine was founded slightly south of Fort Caroline, which was a French settlement. It became the oldest continuously-settled European settlement in the continental United States and played a significant role in the rivalry between European powers in the Americas. The Spanish established this settlement to reduce the threat of French privateers and strengthen Spain's claim to the area.