The Goal and Mission of the Grand Army of the Frontier is to honor the memories and achievements of the late Victorian-era military of all nations between 1858 and 1904, with a particular emphasis on American army on the Western Frontier between 1860 and 1900, though the pursuit and sharing of knowledge, and by actively participating in the hobbies of Cowboy Action Shooting, historical reenacting, living history programs, skirmishing, social events, and other activities while wearing appropriate military attire.
Their big annual event is the National Muster and the 2009 Muster be held on Oct 9-11, 2009 in Ord Nebraska. Participants can stay at historic Ft Hartsuff, (1st 40 to sign up).
For more information about this event and the days up to it, look up this forum thread.
For sign up form, look up http://www.grandarmyofthefrontier.org/GAF%20Muster%20Registartion%202009.pdf
For more information about the Grand Army of the Frontier, look up: www.grandarmyofthefrontier.org