The United States, the third-largest nation in the world by land and water, is divided into six time zones: Hawaii-Aleutian Time, Alaska Time, Pacific Time, Mountain Time, Central Time, and Eastern Time. These time zone boundaries are determined by the U.S. Department of Transportation.
Sometimes a state fits neatly into one time zone, but not always. Over the years, the Department of Transportation has split 15 states: Five were split by Mountain and Central time zones; five were divided by Central and Eastern time zones; two were sliced by Pacific and Mountain time zones; and Alaska was cut into Hawaii-Aleutian and Alaska time zones. The rollout of the time zones is a mirror of how the nation has grown. Here is how your state was founded.
24/7 Tempo has taken a look at the sometimes crazy-quilt nature of the time zone boundaries of the United States to understand how the time zones were determined. We reviewed data from the Department of Transportation, the Federal Register, and reviewed articles from sources such as nationalgeographic.com, mapsofworld.com, and csmonitor.com to compile our list.
The United States was divided into four standard time zones on Nov. 18, 1883, and oversight of the zones was given to the Interstate Commerce Commission (ICC). Congress made the system official with the Uniform Time Act of 1918.
Standardization of time zones was advocated by railroads to improve their scheduling and make their operations safer. Until standardization, each town had its own time. The DOT has been responsible for overseeing time zones since 1967.
The DOT receives several requests each year for changes. Communities have to prove a time zone change would bring an economic benefit. Among the factors the DOT weighs are where people shop, work, and go to school, and the location of transportation centers. Even though the nation’s population has been shifting west and south, the localities generally attempt to move to the time zone to the east, mostly for economic advantages. These are the fastest growing and shrinking states.
To find the states with more than one time zone, 24/7 Tempo reviewed data from the Department of Transportation (DOT), which is responsible for overseeing time zones in the United States. Time zones in the United States are defined in the U.S. Code, Title 49, Subtitle A Part 71. For this story, we also included time zones in Arizona where Navajo Indian Reservation observes Daylight Saving Time and Arizona does not. Population totals for states are from the U.S. Census Bureau’s annual estimates of the resident population for the United States, regions, states, and Puerto Rico: April 1, 2010 to July 1, 2019.