The most extensive study of the history of time zones in Indiana has been conducted by Thomas G. Shanks in his book The American Atlas (197). In 1949, the Indiana General Assembly passed a bill to put all of Indiana in Central Standard Time and ban Daylight Saving Time. However, the law had no enforcement power and was largely ignored by communities that wanted to observe Eastern Standard Time. In 1957, the state legislature passed a law to make Central Time the official time zone of Indiana, but allowed any community to switch to Daylight Saving Time during the summer. Governor Roger D. Branigin asked the USDOT to put all of Indiana back in the Central Time Zone in 1967, and after several hearings, the USDOT divided Indiana between the Central Time Zone and the Eastern Time Zone. Six counties near Chicago (Lake, Porter, LaPorte, Jasper, Newton and Starke) and six counties near Evansville (Posey, Vanderburgh, Warrick, Spencer, Gibson and Pike) were placed in the Central Time Zone with Daylight Saving Time observance. The rest of the state was placed in the Eastern Time Zone without observing Daylight Saving Time.
In 1972, Indiana General Assembly overturned a veto by Governor Whitcomb to place Indiana's northwest and southwest corners in the Central Time Zone during Daylight Saving Time, and place the rest of the state in Eastern Standard Time. Several counties in eastern Indiana (Ohio and Dearborn counties near Cincinnati; and Floyd, Clark, and Harrison counties near Louisville) chose to observe Daylight Saving Time unofficially. In 1991, Starke County was moved from the Central Time Zone to the Eastern Time Zone.
Attitudes began to change in the 1990s when Indiana's complicated time zone situation was considered to prevent economic growth. Some argue that the entire state should move to Central Time while others would prefer that the state revert to non-observance of Daylight Saving Time. Opponents of putting the entire state in a time zone often cite out-of-state cities as their reason for opposition. Supporters of Daylight Saving Time and a common time zone in Indiana often claim that Indiana should adopt the Eastern United States timing system to preserve interstate business with that region.
The confusion caused by Indiana's time zone situation has been featured prominently in popular culture such as an episode of The West Wing. Decades-long debate over Indiana's time zone remains controversial.