Many exhibitions have been held in the vast spaces of U.S. National Guard armories, but the Armory Show refers to the International Exhibition of Modern Art that was organized by the Association of American Painters and Sculptors and opened in New York City's 69th Regiment Armory, on Lexington Avenue between 25th and 26th Streets, on February 17, 1913, ran to March 15, and became a legendary watershed date in the history of American art, introducing astonished New Yorkers, accustomed to realistic art, to modern art. The show served as a catalyst for American artists, who became more independent and created their own "artistic language".
In February 2009 The Art Dealers Association of America (ADAA) presented its 21st annual Art Show to benefit the Henry Street Settlement, at the Seventh Regiment Armory, located between 66th and 67th Streets and Park and Lexington Avenues in New York City. The exhibition began as a historical homage to the original 1913 Armory Show. Starting with a small exhibition in 1994, by 2001, the "New" New York Armory Show, held in piers on the Hudson River, evolved into a "hugely entertaining" (New York Times) annual contemporary arts festival with a strong commercial bent. The 2008 and 2009 Armory Shows did not hold back on the more crude and vulgar works, which are not unknown for the show, which has been less tame in past years. With the 100th anniversary in 2013 on the immediate horizon it is possible that the centennial of the original Armory Show will be celebrated in the 21st century.
The Armory Show, The International Fair of New Art, is the largest contemporary art fair in New York, and one of the largest in the world. It originally started in 1994 as the Gramercy International Art Fair, an art fair held in the rooms of the Gramercy Hotel in New York City, and was founded by four art dealers: Colin De Land, Pat Hearn, Matthew Marks and Paul Morris . The fair quickly outgrew its location and became The Armory Show in February 1999. It was first held at the 69th Regiment Armory , the site of the legendary Armory Show of 1913 that introduced Modern art to America and for which it was named, and is now held annually in Pier 94 on New York City’s west side. In 2007, The Armory Show was bought by Merchandise Mart Properties, Inc.
The event, which lasts four days, has attracted crowds of up to 52,000 and reported sales of up to $85 million. Due to The Armory Show’s success, a number of smaller fairs follow the same schedule. This, in conjunction with other institutions that also schedule special events at the same time, have led to the term “Armory Week.” 
Starting in 2002, The Armory Show has commissioned artists to provide visuals for the fair. These artists have included Karen Kilimnik (2002), Barnaby Furnas (2003), Lisa Ruyter (2004), Jockum Nordström (2005), John Wesley (2006), Pipilotti Rist (2007), John Waters and Mary Heilmann (2008), and British artist Ewan Gibbs (2009). In 2006 The Armory Show began publishing an annual series of prints by the commissioned artists to benefit the Pat Hearn and Colin de Land Cancer Foundation and the Pat Hearn and Colin de Land Acquisition Fund at The Museum of Modern Art.
Some above information from Wikipedia http://en.wikipedia.org/wiki/Armory_Show All links remain active.