National Monument: Castillo de San Marcos - The Oldest Masonry Fort in the Lower 48

Last updated: October 4, 2022

While on a road trip to Florida with my mom, we stopped and spent an entire day in St. Augustine and I’m honestly a little perplexed as to why I didn’t know about this very interesting city! One could easily spend two or three days exploring this area. We visited Castillo de San Marcos (which you’ll read about below), the Fountain of Youth Archaeological Park, the St. Augustine Lighthouse (so cute!), Fort Matanzas National Monument, and Downtown St. Augustine (which has America’s oldest wooden schoolhouse!).

Castillo de San Marcos is the oldest masonry fort in the continental United States, translating to “St. Marks Castle”. For the record, I spent WAY too long researching WHY it was named after St. Mark and I came up with zilch. If you can tell me why, I’d be super appreciative!

A Summarized History

I have read pages and pages about Castillo de San Marcos and pulled the quick and dirty version for you here because, call me crazy, but I think it’s important for us to know things about the country in which we live.

So, back in the 1500s, when Florida was under the Spanish Empire, they started making their claim to the new world in St. Augustine and after a while, had a whole functioning city. They had a wooden fort they used to protect the city and in 1668, an English raid resulting in the city and the fort being majorly damaged by fire. The Governor ordered a new, indestructible, fort to be built and the first stones were laid in 1672, with the completion of the fort ending in 1695 (and I thought my home renovation projects were long). That means at the time of this writing, this castle is 327 years old and I have to admit, it’s a sight to see.

In 1819, Spain signed the Adams–Onís Treaty which ceded Florida to the United States in 1821; consequently, the fort was designated a United States Army base and renamed Fort Marion, in honor of American Revolutionary Warhero Francis Marion.
In 1898, over 200 deserters from the Spanish–American War were imprisoned at the fort. This marked one of the last uses of the fort as an operational base. In 1900, the fort was taken off the active duty rolls after 205 years of service.
In 1924, the fort was designated as a National Monument. In 1933 it was transferred to the National Park Service from the War Department.
In 1942, in honor of its Spanish heritage, Congress authorized renaming the fort as Castillo de San Marcos. As an historic property of the National Park Service, the National Monument was listed on the National Register of Historic Places on October 15, 1966.

We even got to see the drawbridge in action from across the way to let a boat through.

Wondering around this castle and exploring all the rooms was legit fascinating. We even got to see the drawbridge So much history… it would take all day to read the plaques and view all the rooms, and if I’d had the time, I probably would have done just that. Check out some photos I took below, and if you’re interested in even more Florida adventures from this trip, see us explore The Keys, Dry Tortugus National Park, and Monkey Jungle!