Why go
The move from inland Caparra to the harbor explains why the city grew where it did. At El Morro, the bay entrance is the focus; at San Cristóbal, the landward approach matters. The two forts make more sense as parts of one defensive plan than as isolated monuments.
The full story
Juan Ponce de León founded the first Spanish settlement at Caparra in 1508, west of today's San Juan. The settlement shifted to the harbor site soon afterward. In 1521 the new town received the name San Juan Bautista de Puerto Rico. Over time, the names used for the town and the island effectively changed places: San Juan became the city name, while Puerto Rico came to name the island and archipelago. The port's position brought both trade and attacks. English forces led by Francis Drake attacked in 1595, and George Clifford's force took the city in 1598. Dutch attackers sacked and burned parts of San Juan in 1625. These episodes help explain the successive fortifications rather than a single moment of construction. El Morro faced ships entering the bay; later defenses strengthened other approaches and the city walls enclosed the settlement. Walking between the bay side and the Atlantic side of Old San Juan turns that history into a map. The narrow islet and the harbor entrance shaped decisions made over centuries, and the surviving walls show how the city expanded its protection as threats changed.