The General Society of the War of 1812 traces its origins to the huge collection of American militia companies which were called to meet the British thrust at Baltimore following the occupation of the National Capital.  Those veterans led by General Samuel Smith, set great importance upon their record against "Wellington's Invincibles" at North Point on September 12, 1814.
With the loss of the lionized Major-General Robert Ross to tree-hidden American sharpshooters, the British advance toward the city slowed whilst the powerful fleet lay useless against Fort McHenry because of the tremendous amount of blockage which had been dropped into the channel.

By September 18 the enemy withdrew several miles below the harbor's entrance, and Francis Scott Key reached a Baltimore hotel where the final touches were made to his epic poem "The Defence of Fort M'Henry" [sic] to be circulated on Tuesday, the 20th.   Uncertain of the next British move, the jubilant soldiers remained fairly in place and gained the sobriquet "Defenders" from the local citizenry.

On the first anniversary, Tuesday, September 12, 1815, the "Defenders" turned out from their work to witness the laying of the Battle Monument cornerstone and to view the Fort McHenry U.S. garrison and some of Maryland's Fifth Regiment parade in the adjacent streets.  Ever after,  the celebration and remembrance of the veterans and their turning back the British has continued in Baltimore and Maryland with the "Defenders' Day Cavalcade". Also in Baltimore and Maryland, a day to commemorate the "Old Defenders" has been officially designated called "Defenders' Day", which is observed as a "bank holiday ".

In 1841 the Defenders met to establish a more formal organization.  The following year a national encampment was held, with veterans attending from Pennsylvania, Virginia and the District of Columbia.  President John Tyler reviewed the parading veterans.   On the 14th of May 1842 the veterans received their first organizational charter in Maryland recorded in the Circuit court of Baltimore as "THE ASSOCIATION OF DEFENDERS OF BALTIMORE" and had as their purposes the encouraging of love of country, commemoration of the war, defraying of funeral expenses of veterans who were impoverished and the education of their children.
Meanwhile Pennsylvania's veterans met at Independence Hall in Philadelphia, 9 January 1854 (anniversary of the Battle of New Orleans), and perfected the organization of the society of the War of 1812.  As the 19th century drew to a close, the ranks of the 1812 veterans grew thinner.  In 1893 the Maryland group was reorganized to include the sons and male descendants of veterans; it was incorporated in 1893 as The Society of the War of 1812 in Maryland of Baltimore City.  The Pennsylvania Society of the War of 1812 had incorporated in 1892 as The Pennsylvania Society of the soldiers of 1812.   In 1894 the Maryland and Pennsylvania societies met at Independence Hall, along with delegates from similar societies in Connecticut, Massachusetts and New York.

On 14 April 1894 these societies formed the General Society of the War of 1812, with each of the constituent societies becoming a state society.  In time the General Society chartered groups throughout the United States.  For members who do not live in a state having an organization the General Society has a class of members-at-large.