In AD 75 the Romans built a fort where Cardiff Castle now stands. The name Cardiff probably derives from the Welsh Caer Tâf (Fort on the River Taff) or Caer Didi (Didius' Fort), referring to Roman general Aulus Didius. After the Romans left Britain the site remained unoccupied until the Norman Conquest. In 1093 a Norman knight named Robert Fitzhamon (conqueror of Glamorgan and later earl of Gloucester) built himself a castle within the Roman walls and a small town grew up around it. Both were damaged in a Welsh revolt in 1183 and the town was sacked in 1404 by Owain Glyndŵr during his ill-fated rebellion against English domination.
The first of the Tudor Acts of Union in 1536 put the English stamp on Cardiff and brought some stability. But despite its importance as a port, market town and bishopric, only 1000 people were living here in 1801.
The city owes its present stature to iron and coal mining in the valleys to the north. Coal was first exported from Cardiff on a small scale as early as 1600. In 1794 the Bute family – which owned much of the land from which Welsh coal was mined – built the Glamorganshire Canal for the shipment of iron from Merthyr Tydfil down to Cardiff.
In 1840 this was supplanted by the new Taff Vale Railway. A year earlier the second marquess of Bute had completed the first docks at Butetown, just south of Cardiff, getting the jump on other South Wales ports. By the time it dawned on everyone what immense reserves of coal there were in the valleys – setting off a kind of black gold rush – the Butes were in a position to insist that it be shipped from Butetown. Cardiff was off and running.
The docklands expanded rapidly, the Butes grew staggeringly rich and the city boomed, its population mushrooming to 170,000 by the end of the 19th century and to 227,000 by 1931. A large, multiracial workers' community known as Tiger Bay grew up in the harbourside area of Butetown. In 1905 Cardiff was officially designated a city, and a year later its elegant Civic Centre was inaugurated. In 1913 Cardiff became the world's top coal port, exporting some 13 million tonnes of the stuff.
The post-WWI slump in the coal trade and the Great Depression of the 1930s slowed this expansion. The city was badly damaged by WWII bombing, which claimed over 350 lives. Shortly afterwards the coal industry was nationalised, which led to the Butes packing their bags and leaving town in 1947, donating the castle and a large chunk of land to the city.
Wales had no official capital and the need for one was seen as an important focus for Welsh nationhood. Cardiff had the advantage of being Wales' biggest city and boasting the architectural riches of the Civic Centre. It was proclaimed the first ever capital of Wales in 1955, chosen via a ballot of the members of the Welsh authorities. Cardiff received 36 votes to Caernarfon's 11 and Aberystwyth's four.