The Alco RS3 entered production in 1950 replacing its predecessor the RS2. The new model produced slightly more horsepower than the earlier design at 1,600 hp using Alco's commonly problematic 12-cylinder, model 244 prime mover.
From a visual standpoint the RS3 looked almost identical to the RS2. Both had much improved styling over the RS1 albeit it was quite subtle with heavy beveling to corners and edges giving the unit a much more streamlined appearance (because of its good looks some railroads elected to employ theirs in passenger/commuter service).
Instantly beloved by railroads for its versatility and reliability, RS3s began rolling out of Alco's Schenectady shops in the masses.
Perhaps more than any other locomotive the RS3 defined Alco as a locomotive manufacturer offering eye-appealing, classy designs with their trademark belching black smoke.
While the RS1 and RS2 had sold relatively well perhaps it was the RS3's extra 100 horsepower over its predecessor that really appealed to railroads.
While the model 244 proved generally reliable and rugged in its smaller switcher and light road switcher designs (like the RS3) the prime mover simply not been properly researched and developed for heavy-haul use.
As such, the FA and PA models in production at the time experienced significant mechanical issues. This allowed Electro-Motive to gain a notable edge and these problems ultimately resulted in Alco's exit from the market.