The Grand Army of the Republic Civil War Museum and Library was established in 1926 as the repository for the collections of the Grand Army of the Republic, Sons of Union Veterans of the Civil War, and other Civil War related organizations. The original Grand Army of the Republic (GAR) was a fraternal organization founded in 1866 for Union veterans of the Civil War. It was succeeded by the Sons of Union Veterans of the Civil War, a similar organization for male descendants of Union veterans.

The Grand Army of the Republic Civil War Museum and Library is located in the Frankford neighborhood of Northeast Philadelphia, Pennsylvania, and houses a large collection of museum artifacts, some 3,000 books, and approximately 300 cubic feet of archives and manuscripts. The archives includes a fairly complete set of records of GAR Post #2 of Philadelphia, along with the records of several dozen other GAR posts, mostly from the Philadelphia area but several from other parts of the nation as well. There are also the records of other Civil War-related organizations, such as the Philadelphia Camp of the Sons of Union Veterans of the Civil War, Daughters of Union Veterans, Ladies of the GAR, and the GAR Home. The collection also includes some 1860s muster out rolls and other original military service records and a significant amount of manuscript material such as letters, diaries, scrapbooks, and photographs in various formats; prints and lithographs; and complete sets of two Philadelphia newspapers during the Civil War years and individual issues of other Civil War-era newspapers.