Mae lle Cymru yn hanes rheilffyrdd y byd wedi'i hen sefydlu.  Yn 1804,  yng ngwaith haearn Penydarren ger Merthyr Tudful digwyddodd y daith gyntaf yn y byd i'w gyrru gan ager, pan dynnodd locomotif ager Richard Trevithick drên ar hyd tramffordd y gwaith. Agorwyd y gwasanaethau rheilffordd cyntaf i deithwyr rhwng Abertawe a'r Mwmbwls yn 1807
Wales’s place in the history of the global railway is assured.  In 1804 the world's first steam-powered railway journey took place when Richard Trevithick's steam locomotive hauled a train along the tramway of the Penydarren ironworks, near Merthyr Tydfil.  The first passenger rail services were opened between Swansea and Mumbles in 1807.