What was Puerto Rico's strategic value before the 20th century? Objective 1. To explain the strategic importance of Puerto Rico as part of Spain's plan to defend its empire in the Caribbean; 2. To understand the evolution of the Spanish strongholds, in particular San Juan's development from a primitive post to a "plaza fuerte" or stronghold; 3. To examine how the 1898 Treaty of Paris affected Puerto Rico; 4. To learn how historic structures provide a link between the "old" and the "new;” 5. To investigate a historic site in their community. Background Time Period: 1500s-1800s Topics: This less Duration: 90 Minutes.