The Pierce-Arrow Model 51 was a series of luxury cars introduced in 1919. The Model 51, also known as the Series 51, was the successor to the Pierce-Arrow Model 48, and featured an 8.6L inline six engine that generated 75hp. This engine sent drive to the rear wheels via a 4 speed manual transmission to the rear wheels. Body styles included tourer, saloon, and limousine. Production of the Model 51 ended in 1920.