Kentucky's state police force was established on July 1, 1948, under Governor Earl C. Clements, according to the Kentucky State Police. The state police replaced the Kentucky Highway Patrol.
The first Kentucky state troopers were paid $130 per month and reported to commissioner Guthrie Crowe, states the Kentucky State Police. Troopers wore gray uniforms and underwent three weeks of training. During the 1950s, the force purchased its first airplane and began operating unmarked vehicles to patrol Kentucky's highways. While the standard work week for troopers began at 60 hours, by the 1950s troopers were expected to work 40 hours per week.
During the 1960s, the standard patrol cars were changed from black to gray, inspiring the force's nickname, "The Thin Gray Line," though the cars were later changed to blue and white, to white and then back to gray, reports the Kentucky State Police. The agency's first African-American state trooper was hired during the 1960s, and the first female trooper came onto the force during the 1970s. In the 1970s, the state police instituted an information sharing system called the Law Information Network of Kentucky and opened five new forensic labs around the state. During the 1990s, the force instituted drug testing and changed the model of service weapons in use by officers.