Question: In what year was the fort that George Armistead commanded 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 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.

Fort of San Diego: The Fort of San Diego (Spanish: "Fuerte de San Diego" ), formerly also known as the Fort of San Carlos (Spanish: "Fuerte de San Carlos" ) is a star fort in Acapulco, Guerrero, Mexico.  It was built by the Spanish Empire, and it was one of the most important Spanish fortifications along the Pacific coast.  The fort was first built in the 17th century, but was completely rebuilt in the 18th century.  Today, it is an important landmark in Acapulco, and it is open to the public as the Acapulco Historic Museum (Spanish: "Museo Histórico de Acapulco" ).

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.

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

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.

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.

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.

Hungerford Market: Hungerford Market was a produce market in London, at Charing Cross on the Strand.  It existed in two different buildings on the same site, the first built in 1682, the second in 1862.  The market was first built on the site of Hungerford House, next to Durham Yard, the town house of the Hungerford family.  The house had burned down in 1669 as is recorded in the Diary of Samuel Pepys.  It was replaced by a new Italianate market building by Charles Fowler, which opened in 1833.  The new market was unsuccessful.  It was damaged when the adjoining Hungerford Hall burned down in 1854, and was sold to the South Eastern Railway in 1862.  Charing Cross railway station was built on the site and opened in 1864.

Supporting paragraphs: George Armistead Fort McHenry
Answer: 1798