[10][11] The city of Donetsk in Ukraine (then in the Russian Empire), originally 'Hughesovka', was founded by John Hughes of Merthyr in 1870, when he took iron working to the area.

Merthyr and the surrounding areas boast the Grade-I listed Cyfarthfa Castle, the world’s fastest seated zip line, the UK's largest mountain bike park, the largest indoor climbing wall in Wales, national cycle routes and plans for the UK's longest indoor ski slope.

It covered an area of about three hectares, and formed part of the network of roads and fortifications; remains were found underneath the Merthyr Town F.C.

[23] Merthyr was close to reserves of iron ore, coal, limestone, timber and water, making it an ideal site for ironworks.

[25] Starting in the late 1740s, land within the Merthyr district was gradually being leased for the smelting of iron to meet the growing demand, with the expansion of smaller furnaces dotted around South Wales.

[24] However, this was less of a success until the arrival in 1763 of a "Cumberland ironmaster, Anthony Bacon, who leased an area of eight miles by five for £100 a year on which he started the Cyfarthfa Ironworks and also bought the Plymouth Works".

[26] It was the need to export goods from Cyfarthfa that led to the construction of the Glamorganshire Canal running from their works right down the valley to Cardiff Bay, stimulating other businesses along the way.

They often shared routes to allow access to coal mines and ironworks through rugged country, which presented great engineering challenges.

The tramway passed through what is arguably the oldest railway tunnel in the world, part of which can be seen alongside Pentrebach Road at the lower end of the town.

[29] Famously, upon visiting Merthyr in 1850, Thomas Carlyle wrote that the town was filled with such "unguided, hard-worked, fierce, and miserable-looking sons of Adam I never saw before.

It is like a vision of Hell, and will never leave me, that of these poor creatures broiling, all in sweat and dirt, amid their furnaces, pits, and rolling mills.

Throughout May 1831, the coal miners and others who worked for William Crawshay took to the streets of Merthyr Tydfil, calling for reform, and protesting against the lowering of their wages and general unemployment.

Amid great public interest on 21 February 1804, it successfully carried 11.24 tons of coal, five wagons and 70 men over the full distance in 4 hours and 5 minutes, at an average speed of 2.4 mph (3.9 km/h).

By 1932, more than 80 per cent of men in Dowlais were unemployed; 27,000 people emigrated from Merthyr in the 1920s and 1930s, and a Royal Commission recommended that the town's county borough status be withdrawn.

In October 1948, the American-owned Hoover Company opened a large washing machine factory and depot in the village of Pentrebach, a few miles south of the town.

Hoover and other companies targeted Merthyr; its declining coal and iron industries gave space for new businesses to start up there and grow.

The strong growth of employment of women in Merthyr after the Second World War can be seen as a result of the introduction of more light manufacturing and consumer-based business – a stark contrast to the heavy industry in the coal and ironworks which had an almost entirely male workforce.

In 1992, while testing a new angina treatment in Merthyr Tydfil, researchers discovered that the new drug had erection-stimulating side effects for some of the healthy volunteers in the trial study.

[38] In 2006, inventor Howard Stapleton, based in Merthyr Tydfil, developed the technology that gave rise to the recent mosquitotone or Teen Buzz phenomenon.

[39] In September 2021, Merthyr Tydfil County Borough Council announced a bid to apply for city status, to be coordinated by urban economic and social researcher Dr Jane Croad.

[46] However complaints about the show led to an investigation by regulator Ofcom, which noted the programme had been guilty of "unfortunate and avoidable" factual inaccuracies.

[66] Despite the generally small congregations of Anglican churches, St John's thrived: it held two services in English each Sunday and also two in Welsh.

[73] The town's many cultural events include local poets and writers holding poetry evenings and music festivals organised at Cyfarthfa Castle and Park.

[74] Merthyr Tydfil Housing Association, in partnership with Canolfan Soar, has raised funds to turn the Pontmorlais area into a cultural quarter.

The provision of a new gateway railway station building at Merthyr Tydfil is a key strategic aspiration of the new emerging Town Centre Masterplan, providing a significant regeneration impact within the Borough, increasing connectivity and accessibility to the wider region.

These will reduce journey times between Merthyr Tydfil and Cardiff city centre and allow TfW to increase the frequency of services to four every hour.

[86] Stagecoach South Wales operates services in the area, with routes connecting Merthyr to Aberdare, Brecon, Bridgend, Cardiff, Newport and Porthcawl.

The Welsh Government has recently opened a major office in the town[90] near a large telecommunications call centre (T-Mobile and EE, now part of BT Group).

Hoover (now part of Candy Group) has its registered office in the town and remained a major employer until it transferred production abroad in March 2009, with a loss of 337 jobs from the closure of its factory.

After going into liquidation in 2010, the club dropped down three divisions, reverted to the name of Merthyr Town and made Rhiw Dda'r its new home ground.