Also known as:
Shamrock was an independent refiner operating in the US.
The company ultimately merged with Diamond to form Diamond Shamrock.
1933 - Shamrock opened McKee refinery
1950 - Shamrock acquired Saginaw, Michigan refinery from Louis Rose
1954 - Shamrock shut down Saginaw, Michigan refinery
1967 - Shamrock and Diamond merged to form Diamond Shamrock