Portobelo's military structures provided a security cover on the Caribbean part of the Panama harbour whereas the fortifications at San Lorenzo protected the Chagres River at its mouth.

The Chagres River-Cruces access was a combination of the waterway and terrestrial route built as an alternative to the approach to Portobelo via Camino Real and Panama City.

[3][4] In 1586, Juan Bautista Antonelli prepared the plans for the first of the fortifications to secure entry to the Bay of Portobelo and the mouth of the Chagres River, and constructed the same by the 1590s.

[1] Over the centuries, Portobelo developed into a strategic Spanish establishment in the New World as it was well-linked with a stone paved road to Panama city.

[5] The port's importance as a key transshipment location for the Spanish Conquistadors was to temporarily stack the plundered loot of gold and silver from the Incan mines.

In all, 10 different fortifications were built on the hills behind Portobelo port, making it the "most heavily fortified Spanish coastal control point in the Americas".

[4] In 1668, the Welsh Buccaneer Sir Henry Morgan attacked Portobelo, using ladders wide enough to carry 3 men abreast to scale the walls of the fortifications.

In 1688 English Pirate Bartholomew Sharp and French buccaneer La Sound attacked the fortifications and caused different degrees of damage.

[5] For more than two centuries after the last fortifications were built in 1753, there was total neglect of the forts and battlements resulting in vegetation overgrowth, till the Government of Panama decided to restore them.