Danny Boy Oil Company was founded by Donusios “Danny Boy” Terzakis in 1948 when he was only 24 years old. The primary business of Danny Boy Oil was retail and wholesale distribution of gasoline in the Chicago Metro Area. Danny Boy Terzakis pioneered a way of making gasoline sales more attractive by including give-a-ways and other marketing ideas like using bikini clad models to pump the gasoline for the customers. At one point Danny Boy owned and managed more than 200 gas stations.

In 1977 John Terzakis, Danny Boy’s son, assumed a leadership role at the family business and started to branch out from the gasoline industry, expanding the business to include development of real estate and food services.