Short answers, pulled from the story.
The Grand Army of the Republic was founded on the 6th of April 1866, in Decatur, Illinois, by Dr. Benjamin F. Stephenson. It was established on the principles of Fraternity, Charity and Loyalty as a fraternal organization for Union veterans of the Civil War.
The Grand Army of the Republic reached its peak membership of 410,000 in 1890, coinciding with a high point of Civil War commemorative ceremonies and monument dedications.
General John A. Logan, the first GAR Commander-in-Chief, issued General Order No. 11 on the 5th of May 1868, declaring May 30 to be Memorial Day. The order called on GAR members to make the observance annual, effectively establishing the national holiday as it is known today.
At least five US presidents were confirmed GAR members: Ulysses S. Grant, Rutherford B. Hayes, James A. Garfield, Benjamin Harrison, and William McKinley. Chester Arthur, a Union general and the 21st president, has no confirmed record of membership.
Kady Brownell was the first woman known to have been admitted to the GAR, joining Elias Howe Jr. Post #3 in Bridgeport, Connecticut in 1870. She had served at the First Battle of Bull Run and the Battle of New Berne alongside her husband.
The Grand Army of the Republic was formally dissolved in 1956, following the death of its last member, Albert Woolson. The final National Encampment was held in Indianapolis, Indiana in 1949, when only six of the sixteen surviving members were able to attend.