Cyfarthfa Castle itself was built by the wealthy Crawshay family to overlook their hugely successful Cyfarthfa Ironworks. When the family fortune declined, they sold the building to Merthyr Tydfil County Borough Council in 1908. The Museum and Art Gallery opened in 1910.

At the core of the Collection is the work of Penry Williams, who was the finest artist to come out of Merthyr Tydfil. At the height of his powers, the critics compared him to Turner, which is why he is known as ‘the Welsh Turner’. There is also a broad collection of nineteenth and twentieth-century art on display.