With the introduction of jet propulsion during the late 1940's, performance characteristics of military aircraft dramatically changed. As a result, the military became extremely concerned with establishing human tolerance data for pilots, both from the standpoint of aircraft control and possible ejection from disabled aircraft. A project to determine human tolerance information was instituted at Muroc Field (now known as Edwards Air Force Base) in 1948. The tests used a rocket sled mounted on railroad tracks with hydraulic brakes at one end to stop the sled. With this setup, speeds as high as 600 mph were possible.

The tests were conducted by Colonel John Stapp, a physician with an engineering background. The test results were so profound that the data collected had a significant effect on not only aircraft design, but also automobile crash design. In fact, Col. Stapp devoted much of his latter life to automobile crash injury mitigation.

Edward A. Murphy was a 1940 graduate of the United States Military Academy at West Point. During World War II, he saw service in the Pacific as an accomplished aircraft pilot. After the war, he became interested in aircraft design and went to work as a research and development engineer for the Air Force. It was during this period that he became involved with the rocket sled tests at Muroc and the experiments that would result in the naming of his law.

The early tests at Muroc were conducted with a humanoid crash dummy strapped to a seat on the sled. After these preliminary tests, Col. Stapp decided that he would ride the sled to determine actual human tolerance data. Prior to these tests, it was believed that human tolerance was limited to about 15-20 G's.
(That is, 15-20 times the force of gravity). Over time, Col. Stapp survived forces exceeding 40 G's for time periods exceeding one second. These results greatly changed subsequent aircraft design, for it was now possible to eject pilots, if necessary, at speeds well in excess of 600 mph and expect them to survive. Equally important, motor vehicles are now designed to undergo highway accidents, where occupants will survive exposures perhaps as high as 40 G's. These accomplishments had their foundation with the early work at Muroc Field.

The program was not without several trying incidents. In 1949, the accuracy of the accelerometers was questioned. Captain Murphy, in charge of the instrumentation, decided to use a new type of strain gage accelerometer and a test was conducted.