Together with the other Merthyr ironworks - Dowlais, Penydarren and Plymouth - Cyfarthfa made Merthyr the greatest centre of ironmaking in the world from 1800 to 1860.
Ynghyd â gweithfeydd haearn eraill Merthyr - Dowlais, Penydarren a Plymouth - Cyfarthfa a wnaeth Ferthyr y ganolfan gwneud haearn fwyaf y byd rhwng 1800 a 1860.