An old photograph of a South Wales mining valley. Note the pit head to the right and the typical terraced housing. (The Museum of Welsh Life, at St. Fagans near Cardiff, has a row of these small houses all furnished to reflect the different stages of occupation.) 

The row of railway trucks in front of the houses might have carried the famous Welsh "steam coal" which fuelled Britain's industrial and maritime expansion. Steam coal burned with great heat but little flame or smoke and was transported to coal bunkers all over the world for use in British warships and merchant vessels. 

Welsh miners and iron workers became highly valued in US industrial centres like Scranton, Wilkes-Barre, Carbondale and Pittsburgh. Elwyn T. Ashton noted that:
In the decade 1820-1830 only 170 Welsh were recorded as entering the United States as immigrants. By 1850 that figure had gone up to 1261, and in the decade 1851-60 as many as 6319 Welsh had entered as immigrants, most of them "industrial".