Craig Yr Allt Colliery was situated south of Nantgarw village. However, whenever the Taff River flooded, water frequently entered its workings, and it was abandoned in 1878. The sinking of the twin shafts in 1911 reached the
coal seam at a depth of more than 850 yards in 1915, placing them 2000 ft below sea level and making Nantgarw the deepest pit to be sunk in the
South Wales Coalfield up to that time. Having suffered from various geographical issues,
Powell Duffryn designed a development scheme in 1937, but work was suspended when
World War II broke out in 1939. A later project to re-open the colliery was approved by the
Ministry of Fuel and Power in 1946, and after
nationalisation in 1947, the
National Coal Board invested £5 million on modern surface constructions and modern mining methods. Having survived the mass pit closures of the 1960s, the geographical problems meant the closure of the mine working in 1974, and the unit merged with
Windsor Colliery,
Abertridwr, Caerphilly from 1975. By 1979, the combined Nantgarw/Windsor Colliery employed around 650 men, producing over 4,000 tons of coal per week, making a profit of over £0.5 million. The unit lost £7 million in 1981, employing: 142 on development; 131 on the coalface; 197 below the ground; 101 on the surface. In 1982 output declined steeply as a major coal seam at Windsor became unworkable, while in 1984 an overtime ban led directly to the
1984/5 UK miners strike spreading to South Wales. Although profitable post the strike, both sites of the whole unit closed as part of the NCB regional review on 6 November 1986. ==Village today==