In 1946, the Allison Division of General Motors initiated heavy duty transmission operations at its headquarters in Indianapolis, Indiana. Since that time, Allison has become a world leader in the design, development, and manufacture of heavy duty automatics for the world truck and bus market. This paper traces the history of this effort and discusses key innovations and events at Allison over the past 50 years. Included are discussions starting with Allison's history, its first bus transmission in 1946, and first automatic transmission for on-highway trucks in 1954. This is followed by the development of both the second and third generation automatics and the innovations that are incorporated in these generations. The effect of these innovations is expressed in terms of customer benefits and market growth. Lastly, a view of future trends in automatic transmissions is provided.