Cefn Mawr was part of the ancient parish of Ruabon and the area was known as Cristionydd Cynrig (or Cristioneth Kenrick in English). In 1844, most of Cristionydd Cynrig, together with the neighbouring township of Coed Cristionydd became part of the new parish of Rhosymedre.^[3]

Cefn railway station served the village from 1848 to 1960.

Cefn Mawr was formerly heavily industrialised, with large deposits of iron and coal and sandstone, and heavy industry dominated the area in the 18th and 19th centuries. Iron was worked at several blast furnaces and forges throughout the area and coal was mined at pits in Cefn, Plas Kynaston and Dolydd. Stone was cut at quarries above Cefn Mawr. Much of the mineral wealth of the area was exported by canal over the Pontcysyllte Aqueduct on the Shropshire Union Canal, until the railway reached Ruabon in 1855.

In 1867 Robert Ferdinand Graesser, an industrial chemist from Obermosel in Saxony, Germany, established a chemical works at Plas Kynaston to extract paraffin oil and paraffin wax from the local shale. The company later expanded into the production of coal tar, and carbolic acid (phenol). The site soon became the world's leading producer of phenol. In 1919 the US chemical company Monsanto entered into a partnership with Graesser's chemical works to produce vanillin, salicylic acid, aspirin, and later rubber processing chemicals. The site was later operated by Flexsys, a subsidiary of Solutia, but production ceased in 2010. With the closure of the nearby Air Products and Chemicals site at Acrefair, manufacturing in the village has almost disappeared. A large Tesco store was opened in March 2012 on the former site of the village football team, Cefn Druids. After buying this land, Tesco agreed to contribute to the construction of the new football ground located half a mile (1 km) away near the neighbouring village of Rhosymedre.

• Miles Thomas, (1897–1980), former chairman of the British Overseas Airway Corporation.
• Peter Halliday (1924–2012), actor most prominently featured in Doctor Who.
• Gareth Valentine, born 1956, composer, arranger, conductor and musical director known for his works on musical productions in London's West End.
• Neco Williams, born 2001, professional footballer for Nottingham Forest and the Wales national football team.

Tŷ Mawr Country Park is located in the area, and features the Cefn Viaduct, built by Thomas Brassey in 1848 to carry the Shrewsbury and Chester Railway across the valley of the River Dee. The village has two primary schools: an English, Cefn Mawr County Primary School, and a Welsh, Ysgol Min Y Ddol. There is also a public library.

The community has 3 Football Teams Cefn Druids, Cefn Albion and Cefn Mawr Rangers F.C.

• BBC mini-site for Cefn Mawr Archived 4 March 2006 at the Wayback Machine
• 180 Degree Panoramic View of Tŷ Mawr Country Park (BBC) Archived 12 February 2006 at the Wayback Machine (Java Applet Required)
• Historical recollections of Cefn Mawr
• Monsanto website
• NEWI Cefn Druids F.C.
• photos of Cefn Mawr and surrounding area on geograph
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