The Wasp Jr. R-985 was the third engine type designed by Pratt & Whitney Aircraft, following the Wasp R-1340 and Hornet R-1690, all of which were nine-cylinder engines. The Wasp Jr. was designed to compete at lower power and was virtually a Wasp of reduced dimensions, as the details of construction were followed closely throughout. First certificated in January 1930 at 224 kW (300 hp), the Wasp Jr. was designed for light transports, trainers, sport aircraft, and helicopters. A number of models were made, most at 298 kW (400 hp) or higher power.

Powering a wide variety and large number of well known military and commercial aircraft such as the de Havilland Beaver and Lockheed Electra, the R-985 was one of the most successful reciprocating engines ever built in its power class. This artifact was built under license by the Jacobs Aircraft Engine Company of Pottstown, Pennsylvania, and powered a Beech 18 executive transport aircraft.