Question: When was the fort commanded by George Armistead during the Battle of Baltimore first built?

Context paragraphs:
Fort McHenry: Fort McHenry, in Baltimore, Maryland, is a historical American coastal pentagonal bastion fort best known for its role in the War of 1812, when it successfully defended Baltimore Harbor from an attack by the British navy from the Chesapeake Bay September 13–14, 1814.  It was first built in 1798 and was used continuously by U.S. armed forces through World War I and by the Coast Guard in World War II.  It was designated a national park in 1925, and in 1939 was redesignated a "National Monument and Historic Shrine".

George Armistead: George Armistead (April 10, 1780 – April 25, 1818) was an American military officer who served as the commander of Fort McHenry during the Battle of Baltimore in the War of 1812.

Battle Monument: The Battle Monument, located in Battle Monument Square on North Calvert Street between East Fayette and East Lexington Streets in Baltimore, Maryland, commemorates the Battle of Baltimore with the British fleet of the Royal Navy's bombardment of Fort McHenry, the Battle of North Point, southeast of the city in Baltimore County on the Patapsco Neck peninsula, and the stand-off on the eastern siege fortifications along Loudenschlager and Potter's Hills, later called Hampstead Hill, in what is now Patterson Park since 1827, east of town.  It honors those who died during the month of September 1814 during the War of 1812.  The monument lies in the middle of the street and is between the two Baltimore City Circuit Courthouses that are located on the opposite sides of North Calvert Street.  It was sponsored by the City and the "Committee of Vigilance and Safety" led by Mayor Edward Johnson and military commanders: Brig. Gen. John Stricker, Maj. Gen. Samuel Smith and Lt. Col. George Armistead (of Ft. McHenry).

HMS Aetna (1803): HMS "Aetna" was one of the Royal Navy bomb vessels involved in the attack on Fort McHenry in the Battle of Baltimore and the bombardment of Fort Washington, Maryland in 1814, during the War of 1812.  In these actions she was commanded by Richard Kenah.  Prior to this, "Aetna" participated in the second Battle of Copenhagen in 1807 and the Battle of the Basque Roads in 1809.  In both these actions, she was commanded by William Godfrey.

Fort Saint-Jean (Quebec): Fort Saint-Jean is a fort in the Canadian province of Quebec located on the Richelieu River.  The fort was first built in 1666 by soldiers of the Carignan-Salières Regiment and was part of a series of forts built along the Richelieu River.  Over the years, it was destroyed and rebuilt several times, but it is, after Quebec City, the military site that has been occupied non-stop for the longest time in Canada.  The fort is designated as a National Historic Site of Canada, and it currently houses the Royal Military College of Saint-Jean.  The fort has been continually occupied since 1748, and is the core from which the city of Saint-Jean-sur-Richelieu, Quebec grew around.  Fort Saint-Jean played a crucial role during the 1775 American invasion of the Province of Quebec.

Siege of Galle (1640): The Siege of the Portuguese fort "Santa Cruz de Gale" at Galle in 1640, took place during the Dutch–Portuguese and Sinhalese–Portuguese Wars.  The Galle fort commanded 282 villages, which contained most fertile cinnamon lands in southern Sri Lanka It was also an important strategic coastal defense of Portuguese Ceylon.  The Dutch, who were in an alliance with the Kingdom of Kandy, landed an expeditionary force under Commodore Willem Jacobszoon Coster of Akersloot, at the Bay of Galle, on 8 March 1640.  After bombarding the fort for four consecutive days, Dutch troops stormed the fort and secured a victory on 13 March 1640.  The Portuguese garrison, led by Captain Lourenço Ferreira de Brito, mounted a stiff resistance and unexpectedly high casualty rates among Dutch troops gave rise to the proverb “Gold in Malacca, lead in Galle”.  With this victory the Dutch gained access to a large port which they later used as a convenient naval base to attack Goa and other South Indian Portuguese defenses.  They also gained access to the Sri Lankan cinnamon trade and gained a permanent foothold on the island.

George Smathers: George Armistead Smathers (November 14, 1913 – January 20, 2007) was an American lawyer and politician who represented the state of Florida in the United States Senate for eighteen years, from 1951 until 1969, as a member of the Democratic Party.

The Last of the Mohicans (1920 American film): The Last of the Mohicans is a 1920 American film adapted from James Fenimore Cooper's novel of the same name.  Clarence Brown and Maurice Tourneur directed an adaption by Robert Dillon — a story of two English sisters meeting danger on the frontier of the American colonies, in and around the fort commanded by their father.  The adventure film stars Wallace Beery, Barbara Bedford, Lillian Hall and Alan Roscoe.

Mary Young Pickersgill: Mary Pickersgill (born Mary Young; February 12, 1776 – October 4, 1857), was the maker of the Star Spangled Banner Flag hoisted over Fort McHenry during the Battle of Baltimore in the War of 1812.  The daughter of another noted flag maker, Rebecca Young, Pickersgill learned her craft from her mother, and, in 1813, was commissioned by Major George Armistead to make a flag for Baltimore's Fort McHenry that was so large that the British would have no difficulty seeing it from a great distance.  The flag was installed in August 1813, and, a year later, during the Battle of Baltimore, Francis Scott Key could see the flag while negotiating a prisoner exchange aboard a British vessel, and was inspired to pen the words that became the United States National Anthem.

Armistead Monument: The Armistead Monument is a bronze statue of Col. George Armistead, by Edward Berge.

Supporting paragraphs: George Armistead Fort McHenry
Answer: 1798