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Castillo de San Marcos
Society: ASCEMain Category: CivilSub Category: BuildingsEra: 1600sDateCreated: 1672-1695St. AugustineState: FLCountry: USAWebsite:

The fort was constructed of coquina rock. Unique to Florida, the rock consists of millions of seashells cemented together. It proved highly durable and easily absorbed the force of many cannon balls. 

The Castillo de San Marcos was the first permanent European settlement in the continental United States. Originally an outpost of the Spanish Empire, it is the oldest major engineered structure existing in America.

Image Credit: Courtesy Flickr/inazakira (CC BY-SA 2.0)Image Caption: Castillo de San MarcosEra_date_from: 1672
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