(This is a work in progress as of 5 April 2020.)
1872: A&P opens its first Pittsburgh location at 44 Smithfield Street,
Before 1910: P.H. Butler Grocery Company is established.
By 1920: Eagle Grocery Company is established by the Goldstein, Porter, and Chait families.
1920s: OK Grocery Company is founded by the Moravitz and Weizenbaum families.
1928: Kroger acquires the Eagle Grocery Company. The founding families agree not to re-enter the grocery field for three years.
1931: The founding families of Eagle Grocery and OK Grocery join to form a new company, opening the fist Giant Eagle supermarket at 756 Brownsville Road in 1936. Smaller stores continue to operate under the OK Grocery name.
By 1936: The first Streamline Market opens at 7301 Penn Avenue.
1938: P.H. Butler begins operating supermarkets under the Thorofare name. The first seems to have opened at 310 Market Street in downtown Pittsburgh.
1943: P.H. Butler/Thorofare acquires 18 of the 23 Streamline Markets. The remainder rebrand as Victory Markets.
1948: Victory Markets rebrands as Sparkle Markets.
1956: Loblaws acquires Sparkle Markets.