Merthyr Tydfil is a town in southern wales named after the 5th-century Welsh princess Tydfil the Martyr, who was killed there. In the 18th century, Merthyr Tydfil became an industrial town due to its rich natural resources, leading to success in the iron industry. The town's success continued to grow into the 19th century when canals and railroads were built for better transport of iron. Merthyr Tydfil was known as the number one steel and iron town until the 1850s, when manufacturing practices changed and caused the iron industry to move elsewhere. The town experienced an industrial revival after World War II, making Merthyr Tydfil a center of industry once again in the region.
Peter Finch references Merthyr Tydfil in Real Wales, stating: "Wales that might as well be England, including the capital and the northeast and the southern coasts; and Y Fro Efallai where desire and actuality mix, where reality comes in like a short wave signal - Myddfai, Banwen, Merthyr, Pontcanna, Aber out of term time. Trefdraeth when the sun shines. Who is to say that his Wales is any better than mine? Or that mine is more real?" Finch references Merthyr Tydfil in a list of other locations in Wales. Finch uses these different places to reference different regions in Wales and then asks if it makes Wales any more real if you know these places. Merthyr is grouped with other towns in south wales.
Sources: https://www.britannica.com/place/Merthyr-Tydfil-Wales, https://www.historic-uk.com/HistoryUK/HistoryofWales/Merthyr-the-Welsh-…,