1921 -The company adopted the Bulldog as its corporate symbol. The first usage of the Bulldog as a symbol was on a sheet metal plate riveted to each side of the cab. It was first drawn on June 3, 1921 and was released, printed, and specified for the AB chain drive (CD) and dual reduction (DR) carrier drive trucks. The plate shows the Bulldog as two words, i.e., a bull dog chewing up a book entitled "Hauling Costs," "Mack" on his collar, and International Motor Co. of New York. This plate was used much later on M model off-highway trucks, except that the plate then showed Mack Trucks, Inc., Allentown, PA.

1922 - The title of the parent company is changed from International Motor Truck Corporation to Mack Trucks, Incorporated. This change in title was basically made to identify the corporate name more closely with the company's product and lessen any misidentification of Mack products with those of a competitor, the International Harvester Company. The International Motor Company continues as the manufacturing subsidiary of Mack Trucks, Inc. until 1936.

1927 - Over the years there have been few Mack models as famous as the AC model. The Mack BJ and BB models, the first of the "early B Series" introduced in 1927, represented the company's first trucks developed in response to the demand for larger capacity, higher speed haulage. The growing acceptance of trucking as a transport mode required the application of new design and engineering principles, and a variation of sizes and weights to satisfy emerging state regulations. More than 15,000 units were built through 1941.

Mack pioneered the use of power brakes on trucks by using a vacuum-booster system.

1929 - 1944 - During the years from 1929 until 1944, Mack produced 2,601 semi- or full trailers.

Full trailers were of two styles, non-reversible or reversible. Non-reversible trailers had a solidly fastened rear axle arrangement with a draw bar on the front end so that the trailer could be drawn in one direction.

A reversible trailer has axle arrangements similar at each end. Either end could be fastened in a stationary position while the draw bar could be fastened to the other end of the trailer. In this way, either end could be the front of the unit.