Also known as:
1933 - Shamrock opens McKee refinery
1950 - Shamrock acquires Saginaw, Michigan refinery from Louis Rose
1954 - Shamrock shuts down Saginaw, Michigan refinery
1961 - Ultramar opens Holyrood, Nova Scotia refinery
1967 - Shamrock and Diamond merge to form Diamond Shamrock
1971 - Ultramar opens Quebec City refinery
1983 - Ultramar shuts down Holyrood, Nova Scotia refinery
1984 - Diamond Shamrock acquires Three Rivers refinery from Sigmor
1988 - Ultramar acquires Wilmington refinery from Union Pacific Resources
1990 - Ultramar acquires Dartmouth, Nova Scotia refinery from Texaco
1994 - Ultramar shuts down Dartmouth, Nova Scotia refinery
1997 - Ultramar and Diamond Shamrock merge to form Ultramar Diamond Shamrock
1997 - Ultramar Diamond Shamrock acquires North America refining assets of Total (Commerce City; Ardmore; Alma, Michigan)
1999 - Shuts down Alma, Michigan refinery
2002 - Company acquired by Valero