In the first years after the start of the construction of the Baltimore & Ohio Railroad, all cars were hauled by horses. Peter Cooper, who also had interest in the economical fortune of the region, soon wanted to prove that steam power would be superior. The first tests with locomotives imported from Britain were not successful, and so Cooper developed a completely new design. The main consideration was that the new design was smaller, so that it could navigate the curve radii intended for horse-drawn railways.

The locomotive was named “Tom Thumb” after a character of English folklore. It was constructed on a platform around 13 feet in length that stood on two axles. It had a vertical, anthracite-burning boiler with tubes made from gun barrels. Draft was generated by a fan in the stack that was driven by the rotation of the wheels. Two vertical cylinders were mounted behind the cylinders and drove the rear axle. It had around one and a half hp and could haul 45 tons on a grade of 0.7 percent with 15 mph. When it entered service in 1830, it was the first American-built steam locomotive operating on a common carrier railroad.

To prove its performance, it had to compete in a race over eight miles against a horse drawn carriage. Although the blower belt slipped off the pulley so that the locomotive lost power and lost against the horse, it was enough to convince the railroad that steam traction was superior. It laid the foundation of the “Grasshopper” type of locomotives, most of which had two driving axles. The original “Tom Thumb” was scrapped soon since it was not built for commercial service. In 1927, the B&O built a replica for the Fair of the Iron Horse that is basically still in working order today.