McDonald's was headquartered in the Loop until 1971, when it moved to suburban Oak Brook.Cross, Robert. "Inside Hamburger Central ." Chicago Tribune. January 9, 1972. G18. Retrieved September 17, 2009. When Bank One Corporation existed, its headquarters were in the Bank One Plaza, which is now Chase Tower."Contact Information." Bank One Corporation. April 10, 2001. Retrieved March 31, 2010. When Amoco existed, its headquarters were in the Amoco Building, which is now the Aon Center."Contacts." Amoco. February 12, 1998. Retrieved March 31, 2010.
McDonald's was headquartered in the Loop until 1971, when it moved to suburban Oak Brook.Cross, Robert. "Inside Hamburger Central ." Chicago Tribune. January 9 1972. G18. Retrieved September 17, 2009. When Bank One Corporation existed, its headquarters were in the Bank One Plaza, which is now Chase Tower."Contact Information." Bank One Corporation. April 10, 2001. Retrieved March 31, 2010. When Amoco existed its headquarters were in the Amoco Building, which is now the Aon Center."Contacts." Amoco. February 12, 1998. Retrieved March 31, 2010.