The State of Pennsylvania wanted to celebrate the 50th anniversary of Gettysburg and honor all the surviving veterans by bringing them to the Gettysburg battlefield for a massive reunion.
The State of Pennsylvania provided tents and food for the 65,000 Confederate and Union veterans who arrived for the reunion in the summer of 1913. No one had ever fed this many people before so a new system of food supply and delivery had to be improvised.
Cuts of fresh beef were chilled and boned in multiple Pennsylvania packing houses. The meat was packed in lined boxes. The cases of chilled and frozen meat were shipped by rail to Gettysburg, where they were distributed to the small mess kitchens located throughout the camp site.
Several years later during WW1, supply shortages forced Army Quartermaster personnel to find new and more efficient methods for packing and crating on board cargo ships going to Europe.
In 1918, Lieutenant Jay C. Hormel- later President of George A. Hormel and Company- was charged with developing a large-scale system of boneless beef production and emulated the Gettysburg reunion method. After the War, the next step was the the advent of the popular consumer product- SPAM.
You can join the Sons of Cenfederate Veterans, the Sons of Union Veterans of the Civil War, or you can simply dig in to the delicious taste of Spam.
Source U.S. Army Quartermaster Museum website