February 21, 1804

Penydarren locomotive

Trevithick's locomotive hauls a loaded train from Penydarren to Abercynon

Seventy men climbed onto the five iron wagons for the trip, and the party had to stop and cut down trees and shift large rocks off the route.

Nine and three-quarter miles down the Merthyr Tramroad

On 21 February 1804 Richard Trevithick's high-pressure steam locomotive pulled a train along the Merthyr Tramroad from Penydarren Ironworks at Merthyr Tydfil to the canal junction at Abercynon, a route of 9¾ miles.

Five wagons carried ten tons of iron, with seventy men riding on them — museum accounts describe them as men who hitched a ride, not customers of a service.

The loaded run was made to show that smooth iron wheels could grip smooth rails hard enough to haul a useful load, and to settle a wager involving the Penydarren proprietor Samuel Homfray.

Four hours five minutes, two hundredweight of coal

Trevithick's letter written the next day says the journey took four hours and five minutes and that the party had to cut down trees and remove large rocks from the route.

He reported the engine approaching five miles per hour while moving — its speed in motion, not its average across an obstacle-delayed trip — burning two hundredweight of coal, and reaching Abercynon without taking on more boiler water.

On the attempted return a small bolt fastening the axle to the boiler broke, released the boiler water and kept the engine from coming back until the following evening.

The steam worked; the rails did not

Trevithick wrote that the gentleman who had bet 500 guineas against the engine rode along and conceded.

The tramroad had been laid for horse-drawn wagons on brittle cast-iron plates, and the heavy, unsprung locomotive repeatedly broke them; the engine was converted back to stationary work within months.

The safest claim for the day is the first authenticated steam-hauled train journey carrying a useful load: this machine had already been placed on the tramroad on 13 February, and whether Trevithick's earlier Coalbrookdale locomotive ever ran remains uncertain.

Sources

Researched 24 Aug 2026 6 sources not yet audited

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What the sources leave uncertain

The 21 February loaded journey is securely dated by Trevithick's letter of 22 February referring to “yesterday.”
Testing had begun earlier: Trevithick wrote on 15 February that the engine was fired without wheels on 11 February and placed on the tramroad on 13 February.
The safest superlative is “first authenticated or recorded steam-hauled train journey carrying a useful load.” An earlier Trevithick locomotive was built at Coalbrookdale, but whether it ran is uncertain, and some authorities call the 13 February Penydarren test the first attested locomotive run.
Accounts disagree about the wager's opposing party and exact conditions; Trevithick's contemporary letter securely states only that a gentleman who bet 500 guineas against the engine rode along and conceded.