The Grand Army of the Republic ceased operations in 1956 but it's work and it's successor is the organization, The Sons of Union Veterans of the United States of America, http://www.suvcw.org/id.htm. Begun in 1881, it was founded by the GAR to continue the traditions of the GAR once that organization no longer was in operation. The organization's web site includes an online database where you can search for a Civil War soldier's grave through their National Graves Registration Database. A search for one of my in-law's ancestors, Carlisle Snider, brought up his birth and death date, his unit, branch and state of enlistment, his rank, dates for his enlistment and his discharge. A section entitled "Miscellaneous Notes" included his birth place and his cause of death. The cemetery he is buried in, including the lot number is also included in this description. Finally, the GAR post he belonged to and what grave markers are on his headstone are also included. Cemetery markers can be an important clue in identifying what organizations your ancestor belonged to. When looking at the headstone of a Union soldier, see if the letters "GAR" are found on the headstone, this will identify him as a member.
The Library of Congress', research guide, Fraternity, Charity, and Loyalty (http://www.loc.gov/rr/main/gar/) includes historical information about the GAR, state lists of GAR posts and bibliographical information on auxiliary camps to the GAR including the Women's Relief Corps, Ladies of the Grand Army of the Republic, Daughters of Union Veterans of the Civil War, and Sons of Union Veterans of the Civil War. This guide is an important resource for learning more about the history and impact of this veteran's organization.
The Grand Army of the Republic Museum and Library is located in Philadelphia, Pennsylvania and you can access their web site at http://garmuslib.org/ . The Library does allow researchers access to their materials, which includes post records. A list of available post records can be found on their web site. You can also write to the library with a research request. A history of the GAR and other historical information, including a description of the GAR badge can be found on this web site. This badge description can help you in identifying vintage photos of possible union veterans in your family.
A list of GAR posts in New York are available at http://library.morrisville.edu/local_history/sites/gar_post/index.html. This web site also includes names of those who were members of the GAR in Madison County, New York. Other resources on this web site include links to other GAR web sites for New York and nearby states. There is a list of GAR posts for Illinois at the web site for Illinois in the Civil War at http://www.illinoiscivilwar.org/gar.html . Resources for soldiers attached to a GAR post in Missouri can be found at http://home.usmo.com/~momollus/MOGAR.htm. Posts for Iowa, can be found at http://members.aol.com/grandarmy/page155.htm. For Michigan GAR posts, consult http://www.suvcwmi.org/gar/mi.pdf and its home page at http://www.suvcwmi.org/. A bibliography covering the GAR in Kansas and Civil War veterans is available of the Kansas State Archives site at http://www.kshs.org/research/collections/documents/bibliographies/military/garbib.htm. An additional a bibliography organized by state can be found at the web site for Norcott Genealogical Publications, http://www.ngpublications.com/Bibliography%20of%20G.A.R.%20indexes.htm. They are also in the process of publishing some transcripts of GAR death rolls.
The New York State Archives includes 83 boxes of GAR records from posts in New York State. You can find a description of this collection at http://www.archives.nysed.gov/a/researchroom/rr_mi_GAR_guide.shtml. One will find post minutes, correspondence, regimental histories, and photographs. This resource would provide a descendent with rich material for better understanding a Civil War veteran and GAR member. These records are not available on microfilm or interlibrary loan so you will need to either see them in person, hire a researcher, or request copies from an Archivist at the New York State Archives.
If you are interested in reading more about the auxiliary organizations to the GAR, which in turn might help you learn more about your female ancestor, check out the National Organization Ladies of the Grand Army of the Republic at http://www.rootsweb.com/~nlgar/home.html. History, links and resources will help you in a quest to learn more about the different GAR auxiliaries. Information also exists on this web site and its links for becoming a member of these auxiliaries, some of which do not have an ancestry requirement.