First steam locomotive to run on rails

The first steam locomotive to run on rails was built by engineer Richard Trevithick at Penydarren Iron Works in Merthyr Tidfil, Wales, and first ran on 21 February 1804.

Designed as a "high-pressure steam tram", on its first journey along the Merthyr Tramway it hauled 10 tons (10,000 kg) of coal and 70 men in five wagons along the 9.5 miles (15.2 km) from Penydarren Iron Works to the junction with the Merthyr Canal at Navigation (Abercynon), Wales.

The locomotive’s eventual downfall was its weight. At approximately 5 tons (5,000 kg) it was too heavy for the cast-iron "L" section plates used in 3-ft (0.9-m) lengths as rails, which broke under the load. It ended its days as a stationary engine providing steam to drive factory machinery and was eventually broken up.

Today, a full size replica of the Penydarren locomotive is on display at the National Waterfront Museum in Swansea, Wales.