Castillo de San Marcos National Monument is in St Augustine, Florida. Park area is about 20-acres.  It is located north of the central plaza and fronts Matanzas Bay. The Spanish strategically built it as the northernmost outpost of Spain in the US. Its main purpose was to defend the city from pirates. It was at the northern part of the city to control both the land and marine ingress and egress routes.

St. Augustine is a low lying, sandy city in the eastern coastal plain of Florida. There are barrier islands around it, and on the western side of the city is the San Sebastian River which fortuitously created a natural boundary. Spanish built a seawall on the eastern side. The Park is irregularly shaped rolling, grassy area and has a few trees. Flat grounds around the fort leads to the glacis, which slopes upward toward the fort.  Western boundary of the fort follows the A-l-A.

There is ample paid-parking space, seven-days a week. However it’s usually full by early morning: show up early. Area is popular with joggers, tourists, and pigeons! At the entrance, just before the ticket station are several benches, facing the bay. A gnarly tree stands guard to keep those sitting on the benches company but fails to provide any shade. It does add character to the images though!

Here is an excerpt from NPS’s Historic Resource Guide: http://npshistory.com/publications/casa/hrs.pdf

“During the first century of the Florida settlement, the Spanish built nine different wooden forts for the defense of the colony. Each of these had a short life span due to the ill effects of time, weather, and insects on the structures. Enemy attacks destroyed the forts that were not eliminated by natural forces. The likelihood of attack and the shortage of food and supplies most threatened the safety and stability of the colony. Settlers made few attempts to farm the land around St. Augustine because of poor soil conditions and the threat of Indian attack on those who ventured too far from the settlement. Except for produce raised in small plots around the houses, all of the colony’s food, clothing, and other necessities came from Mexico and Habana, Cuba. Because supply shipments were often detained in Mexico and occasionally lost at sea, the residents of St. Augustine were often hungry and poorly clothed. Fear that the pirates would return to claim the city, which they had not destroyed, led the colonial governor to request aid from officials in Spain and Mexico. The Spanish queen approved the proposal for construction of a masonry fortress at St. Augustine, and in 1672 the first stone was laid for Castillo de San Marcos”

In terms of the construction itself:

In 1669 Queen Regent Mariana of Spain approved the construction of a masonry fortress in St. Augustine and sent the colony’s newly appointed governor, Manuel de Cendoya, to Mexico to obtain the necessary funds. Cendoya arrived in St. Augustine in 1671, after stopping in Havana to recruit masons, stonecutters, and lime burners to aid in construction. In Cuba he also acquired the services of Ignacio Daza, an engineer, and Lorenzo Lajones, the master of construction. Preparations for construction began in 1671 as blacksmiths and carpenters made the necessary tools and implements for quarrying and transporting stone to the construction site. Coquina, a soft limestone made of cemented seashells, was locally available on Anastasia Island and provided an adequate material with which to build the fortress. Lime kilns were built in St. Augustine to convert oyster shells into lime for construction. On October 2, 1672, Cendoya and other royal officials broke ground for the foundation trench of the fort, and several weeks later the first stone was laid. Local Indians, convicts, AfricanAmerican slaves, and occasionally Spanish soldiers labored alongside the skilled workers imported from Cuba.

The entrance to the fort is guarded and gates can be lowered at will.

Inside you enter the rectangular courtyard. From there you can access all the rooms, offices, supply room, and residential quarters. The stairs lead to the rooftop.

Castillo de San Marcos is a bastioned masonry fortification located north of the colonial town of St. Augustine. The Castillo is built around a square plaza, the sides of which measure 320 feet, and has diamond-shaped bastions projecting outward at each comer. The coquina walls of the Castillo are thirty feet high, ten to fourteen feet thick at the base, and five feet thick at the top. Vaulted casemates support the wide terreplein, and embrasures at intervals along the top of the wall provided openings through which cannon could be fired.

The water battery comprises the east side of Castillo de San Marcos between the curtain wall and the seawall. This area was infilled by the U. S. Army Corps of Engineers between 1842 and 1844 to permit the placement of guns facing the harbor. The water battery is constructed of earth and coquina stone. The seawall protects the fort from the waters of Matanzas Bay. Originally built by the Spanish, the seawall was substantially reconstructed by the Army Corps of Engineers between 1833 and 1844. The coquina structure is faced with granite to the high water mark. The hot shot furnace was built in 1844 on top of the water battery. The stuccoed coquina furnace measures nine feet long and eight feet wide, and the chimney is eleven feet high.

http://npshistory.com/publications/casa/hrs.pdf

In the soldiers’ quarters you find cots to sleep, a small cooking and dining area.

There is even a small church.

An even a prison.

The officers quarters were better appointed.

There is a central supply room that stored provisions.

Several of the rooms now contain informational displays about the prominent individuals who were connected with the fort.

From the rooftop, you can see all around it.

In 1924, President Calvin Coolidge, acting under the authority of the Antiquities Act of 1906, declared five forts, including Fort Marion and another Spanish colonial fortification, Fort Matanzas, to be national monuments.

http://npshistory.com/publications/casa/hrs.pdf

This is a not-to-be-missed destination on the historic coast in Northeast Florida!