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Fort Snelling, Minnesota -

Fort Snelling's distinguishing architectural feature is the imposing round tower that would have served as a formidable defensive position during the American Civil War. Set on the bluffs overlooking the confluence of the Minnesota and Mississippi Rivers, the fort was strategically important and remained active for over 100 years. It's preserved as a National Historic Landmark.

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Fort Vancouver, Washington -

Established in 1824 by the Hudson's Bay Company, Fort Vancouver served as a fur trading post rather than a defensive facility. At the height of operations, the fort was the command center for 34 outposts, 24 ports, six ships, and 600 employees. It's open to the public as the Fort Vancouver National Historic Site.

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Fort Gaines, Alabama -

Built on Dauphin Island, Fort Gaines began operations in 1821. The stronghold played a significant role in the Battle of Mobile Bay during the American Civil War. Open to the public, the site is considered to be one of the nation's best-preserved Civil War-era masonry forts.

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Fort McHenry, Maryland -

Fort McHenry, which dates back to 1798, survives as a fine example of a coastal pentagonal bastion fort. It is best known for its role in the War of 1812, when it successfully defended Baltimore Harbor from an attack by British naval forces on September 13–14, 1814. The victory and the garrison flag flown over the fort afterwards inspired Francis Scott Key to write the poem 'Defence of Fort M'Henry' that was later set to the tune 'To Anacreon in Heaven,' and subsequently became known as 'The Star-Spangled Banner,' the national anthem of the United States.

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Fort Union, New Mexico -

Preserved as the Fort Union National Monument, some of the foundations of this adobe-style frontier outpost date back to 1851. Three forts were built on this site, the third remaining active until 1891. Set adjacent to the evocative ruins is a visitor center with exhibits about the fort and a film about the Santa Fe Trail.

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Bent's Old Fort, Colorado -

Operational from 1833, Bent's Old Fort was built as a commercial venture where trappers would trade buffalo robes with Southern Cheyenne and Arapaho Plains Indians. For much of its 16-year history, the fort was the only major white settlement on the Santa Fe Trail between Missouri and Mexico. The station was destroyed in 1849, but has been carefully reconstructed as a National Historic Site, and visitors are welcome.

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Castillo de San Marcos, Florida -

Commissioned in 1695, Castillo de San Marcos on the western shore of Matanzas Bay in St. Augustine is the oldest masonry fort in the continental United States. After 251 years of continuous military possession, it was deactivated in 1933. Since then, it has served as one of the city's most popular tourist attractions.

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Fort Halifax, Maine -

A single wooden blockhouse is all that remains of Fort Halifax, a British colonial outpost that was set on the banks of the Sebasticook River near Winslow. The surviving structure dates back to 1754, making it the oldest example of its kind in the country. It can be admired as a National Historic Landmark.

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Fort Wilkins, Michigan -

Completed in 1844 but since restored, Fort Wilkins was conceived as an army military outpost essentially to maintain law and order between miners and local Native American tribes during the chaotic copper rush of the mid 19th century. Tourists today can visit the garrison as part of a tour within the Fort Wilkins Historic State Park, located in Grant Township.

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Fort Sumter, South Carolina -

Construction on Fort Sumter began in 1829 and was still incomplete in 1861 when the Battle of Fort Sumter began the American Civil War. Built on a sandbar, it provided Charleston with a formidable defense. It is open to the public as part of the Fort Sumter and Fort Moultrie National Historical Park.

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Fort Churchill, Nevada -

The ruins of Fort Churchill stand as a reminder of the site's original purpose as a US Army garrison built in 1861 to protect early western settlers and guard the Pony Express mail service. The site is preserved as being archaeologically significant, and forms the centerpiece of the Fort Churchill State Historic Park.

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Fort Gibson, Oklahoma -

Fort Gibson guarded the American frontier in Indian Territory from 1824 to 1888, essentially maintaining the peace between the Osage and Cherokee tribes in the area at the time—a responsibility it maintained for over 60 years as no massacres or battles occurred there. The visitor center features a museum, and the site hosts special living history events and programs.

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Fort Ticonderoga, New York -

Set on the south shores of Lake Champlain in New York state, Fort Ticonderoga was constructed by French-Canadian forces during the Seven Years' War. Completed in 1758, the fort saw action again during the American Revolution in May 1775.

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Fort Morgan, Alabama -

Perched at the tip of Mobile Point, this historic masonry pentagonal bastion fort commands a grand position overlooking the bay. After its commission in 1834, Fort Morgan was described as the finest example of military architecture in the New World. It remained active until 1944 and is today maintained by the Alabama Historical Commission.

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Fort Delaware, Delaware -

Constructed on Pea Patch Island in the Delaware River, Fort Delaware was still under construction when it saw action during the American Civil War, serving as a prison for captured Confederate soldiers. Today the site operates as a living history museum and is an appealing tourist attraction.

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Fort Point, California -

Completed just before the Civil War by the US Army, Fort Point was built to defend San Francisco Bay against hostile vessels. The garrison is a very popular visitor attraction, as it sits almost directly under the Golden Gate Bridge.

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Fort Independence, Massachusetts -

Dating back to 1634, Fort Independence, a granite bastion set on Castle Island in Boston Harbor, has the distinction of being one of the oldest continuously fortified sites of English origin in the United States. Today the site is preserved as a state park facility.

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Fort Massachusetts, Mississippi -

Planned and built in the wake of the 1812 War as part of an extensive system of masonry fortifications for coastal defense, Fort Massachusetts was used by both Union and Confederate forces during the American Civil War. The fort was last active in 1903. It sits on West Ship Island along the Mississippi Gulf Coast and is managed by National Park Service.

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The Alamo, Texas -

The historic Spanish mission originally known as the Misión San Antonio de Valero later became a garrisoned fortress, shortly after which it acquired its more familiar name, Alamo. It was the site of the infamous Battle of the Alamo in 1836 and today stands as one of the most visited museums in the United States.

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Fort Boonesborough, Kentucky -

Named for its founder, the celebrated frontiersman Daniel Boone, Fort Boonesborough dates back to 1775. The settlement served as an outpost during the American Revolutionary War, and also saw action in the Civil War. It has been reconstructed as a working fort, complete with cabins and period furnishings, and is set within the Fort Boonesborough State Park.

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Fort Phil Kearny, Wyoming -

Located in northeastern Wyoming along the Bozeman Trail, Fort Phil Kearny was built in 1866 as a US Army outpost during the Frontier Wars, ostensibly to protect prospective miners from attack by Lakota and Cheyenne peoples. Now maintained as the Fort Phil Kearny State Historic Site, the reconstructed stockade features a visitor's center with exhibits, videos, and a bookstore. Self-guided tours of the fort grounds and outlying sites can be taken.

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Fort Stevens, Oregon -

Fort Stevens was constructed in 1863 to defend the mouth of the Columbia River during the American Civil War. Interestingly, Fort Stevens was the first military installment in the contiguous United States to come under fire during the Second World War, fired upon by a Japanese submarine on June 21, 1942. The site todays is preserved within Fort Stevens State Park.

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Fort Robinson, Nebraska -

Established in 1873 and intended only as a temporary encampment during the Frontier Wars, Fort Robinson became the site of the Red Cloud Agency, an Indian agency for the Oglala Lakota as well as the Northern Cheyenne and Arapaho indigenous peoples until 1877. The fort today is managed by the Nebraska Game and Parks Commission.

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Fort Smith, Arkansas -

A fort has stood on this site since 1817, the first one commissioned before the area was established as part of Indian Territory. The second fort is what you see today, built in 1838 as a supply depot for other forts within the territory. The town of Fort Smith developed around the garrison, which is maintained as a National Historic Site.

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Fort Pulaski, Georgia -

Fort Pulaski still bears the scars of Union Army artillery bombardment during the American Civil War after it the garrison was overtaken by Confederate soldiers as Georgia seceded from the Union in 1860. Eventually retaken by Northern forces, Pulaski became a prisoner-of-war camp. The fort is open to the public as a National Monument.

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Fort Macon, North Carolina -

Fort Macon State Park is the second most visited state park in North Carolina, with tourists drawn to the fully-restored Fort Macon. The stronghold is noted for the 1862 siege that eventually led to the raising of the white flag over the garrison by beleaguered Confederate forces.

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Fort Tejon, California -

The isolated US Army outpost that is Fort Tejon was active for 10 years, from 1854 to 1864. The fort's location protected the San Joaquin Valley from the south and west, its mission to suppress stock rustling and protect settlers from attacks by discontent Californios (pre-statehood residents), and Native American tribes. The buildings have been restored and preserved as part of the Fort Tejon State Historic Park.

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Fort Sheridan, Illinois -

Fort Sheridan serves as an interesting example of how a modern urban settlement can be incorporated within the fabric of a historic military installation. Constructed during the late 1880s, Fort Sheridan was originally built as an army post to protect Chicago's commercial interests. Officially closed by the Department of Defense in 1993, the building was repurposed as a residential development while maintaining much of the fort's architectural integrity. Parts of Fort Sheridan, however, have been designated as a National Historic Landmark District, preserving officers' quarters, barracks, stables, a drill hall, water tower, and many other institutional buildings.

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Fort Verde, Arizona -

Fort Verde was a base for General Crook's US Army scouts and soldiers in the 1870s and 1880s during the Apache Wars. The site today serves as a living history museum run under the auspices of the Fort Verde State Historic Park.

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Fort Donelson, Tennessee -

Fort Donelson was built in early 1862 by the Confederacy to control the Cumberland River, a vital waterway that led to the heart of Tennessee. Shortly after its completion, it was taken by Union forces during the Battle of Fort Donelson. What remains of the fort is incorporated into the Fort Donelson National Battlefield. 

Sources: (Smithsonian Magazine) (Biography) (History)

See also: Proposed US states and territories that never were

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