A4061 road

The area was rural and sparsely populated until the mid 19th century, when the discovery of coal led to a major industrial boom. The geography of narrow river valleys sandwiched between mountains meant that land space was at a premium, with roads and railways running along limited land space.[8] With relatively little sunlight reaching the valley floors, the local climate in the valleys was depressing. Visiting a town in a neighbouring valley, only a few miles away as the crow flies, could involve a 30-to-40-mile (50-to-65-kilometre) round trip.[9] The A4061 was typical of this, and around 1900 it was a dead end road from Bridgend to Nantymoel, requiring a detour via the Ogwr Fach Valley and Tonyrefail to reach the Rhondda Valley.[10]

The downturn of the coal mining industry after World War I hit the Rhondda particularly hard due to its isolation and lack of access, with high unemployment by the 1920s.[11] In 1924 a series of new mountain roads, to connect isolated valleys, was proposed, including a new through route from Bridgend to Hirwaun via the Rhondda.[12] As well as providing unemployment relief and connecting communities, Glamorgan County Council hoped the better access to the mountain summits would provide recreation, which Lord Temple described as "a playground for all time for those people".[9] The Leader of the Opposition and Labour leader Ramsay MacDonald was particularly keen for the road to be built, knowing it would be good for local economy as well as communications, and he was keen to find ways of moving the economy of South Wales valleys away from the monoculture of coal mining.[13] In addition to the A4061, the A4107 to Abergwnfi and a mountain road from Llyn Fawr to Maerdy in the Rhondda Fach valley were planned as part of the same project.[14] The total estimated cost of the mountain roads, including neighbouring routes was around £400,000 (equivalent to £24,271,000 in 2021), of which 75% was to be paid by central Government and 25% by Glamorgan County Council.[15]

William Jenkins campaigned for the A4061 to be completed.

The road schemes were designed by Ministry of Transport engineer and surveyor George Macpherson,[16] with a standard planned width of 20 feet (6.1 m), with an additional 5 feet (1.5 m) on one side for pedestrians.[14] The workforce was drawn largely from unemployed miners, and the mountain sections were quickly built.[7] About halfway through construction, funding was withdrawn and work halted, though pressure in Parliament, particularly from MacDonald and Sir William Jenkins, ensured there would be a commitment to finish the road in 1928.[13][17] By 1929, £356,431 (now 23,053,000) had been spent on constructing 32.29 miles (51.97 km) of new road (including the A4107 and all connecting links).[14] The Bwlch-y-Clawdd section opened at the end of 1928,[7] while the Rhigos Road section, from Treherbert to Hirwaun, delayed by financial constraints, opened on 4 November 1929.[18] Herbert Morrison, Minister of Transport, visited the works in 1930 and was impressed by the progress and effort expended in the project.[19] The link road from Llyn Fawr to Maerdy was never built.[14]

The landscape at the northern end of the A4061 has been extensively used for open cast mining, which remains an active industry.[20]

In 2013, a large sink hole appeared on the Rhigos Mountain Road section. The road was shut for several days for repairs.[21] In 2016, Rhondda Cynon Taf County Borough Council announced a £1.25 million resurfacing package for the A4061 between Treherbert and Hirwaun. The road was closed for three weeks while the council laid around 6,000 tonnes of tarmac.[22][23] In August 2018, the Rhigos and Bwlch sections were both closed because of a burst water main and essential remedial works respectively.[24]