Detroit’s Continental Motors, which was once one of the largest independent manufacturers of automotive engines, built the Continental A-40 opposed engine. An advantage of horizontally-opposed engines is better forward visibility than radial or V-type engines. The A-40 was the predecessor of a long line of successful horizontally-opposed Continental engines built for general aviation and military aircraft and powered the Piper Cub and other aircraft such as the Taylor Cub E-2 and Taylorcraft Model A. Today opposed engines have replaced all other types of piston engines for various reasons, including fewer cylinders for equal power and smooth running.
National Air and Space Museum, Smithsonian Institution