Before the United States became independent, wars plagued North America, as the British, French, and Spaniards fought for control of the early colonies, with Native Americans sometimes fighting alongside them or launching their own offensives. To protect their lands, the European settlers took a page from the history books, constructing hundreds of forts, as they battled for control of the New World.

It wasn’t a new idea: Civilizations across the globe have built defensive walls to protect their cities from invasion and conquests for thousands of years, dating back at least to 4,700 B.C. in Neolithic Europe. (These are the 15 longest sieges in military history.)

To determine the oldest forts built in what is now the United States before it became a country, 24/7 Tempo consulted websites including Legends of America, Military History Fandom, and the National Park Service to find military fortifications that were built prior to 1775. In most cases, the original forts have not survived intact, but in addition to some surviving structures, the sites contain ruins, reconstructed facilities, or historically accurate replicas on the original fort grounds. (The list is not exhaustive.) Note that many of these forts remained in use after American independence.

Click here to see the oldest military forts built before America was a country

Along with defending seaports from foreign navies and deterring attacks on the frontier, these forts were also the sites of important historical events, including the signing of treaties, visits from famous figures, and – in the case of Fort Johnson – the first raising of the South Carolina state flag. (Here’s how every war In U.S. history ended.)

Some of the fort sites are now located in city or state parks, often with visitor centers, museums, and programs of events. However, some sites may be temporarily closed due to storm damage, flooding, or archaeological work.