The Grand Army of the Republic (GAR) was a fraternal organization of honorably discharged Union Civil War veterans. Some of their rituals were based on Freemasonry. The GAR was founded in 1866 by Benjamin Franklin Stephenson in Decatur, Illinois. By 1890 they had 409,000 members. The GAR was involved in charity and politics, and they lobbied for soldiers homes and pensions. They also began the tradition of Decoration Day on May 30th, now called Memorial Day. Five presidents were members of the GAR: Ulysses S. Grant, Rutherford B. Hayes, James Garfield, Benjamin Harrison and William McKinley. The last GAR member, Albert Woolson, died in 1956 at age 109 (although census research indicates he may have been 106 or 108). He was also the last undisputed surviving Civil War veteran on either side.
For help finding Civil War records see: Online Civil War Records, Indexes and Rosters of Soldiers