Before the Industrial Revolution and the coming of coal mining in the South Wales Coalfield the valley was rural and farmed.

In the Welsh language, ystrad is a wide flat bottomed valley and mynach means "monk".

As there is a lack of evidence for monks settling in the area, the word may have been the name of a tributary of the Rhymney River.

[4] It has been suggested that, rather than referring to a monastic institution, manach is man "place" + -ach, a suffix associated with the names of marshy floodplains, also found in nearby Llanbradach and Llancaiach.

Other notable buildings and structures are the Ystrad Mynach railway station, the viaduct, a sculpture to commemorate the areas industrial heritage, a community hospital, a number of schools, and the Beech Tree, Coopers Arms and Ye Olde Royal Oak pubs.

From 1927 to 1996, Ystrad Mynach hosted the 'F' division headquarters of Glamorgan Constabulary (from 1968, South Wales Police).

They are socially graded houses – ranging from two-up two-down, to a five-bedroom manor in Park Lane with adjoining servants' quarters.

[citation needed] In February 2018, the Beech Tree Fish Bar was severely damaged in a car crash, and the incident made national news.

It is a Grade II listed building, built in 1855–1857, by architect John Norton, for Revd George Thomas whose family were locally important landowners from Llanbradach.

[19] Caerphilly County Borough Council has its main offices at Penallta House in the Tredomen area of Ystrad Mynach.

Much of the boundary between the two parishes was the stream called Nant Caiach (roughly following Nelson Road, the A472), with Gelligaer to the north and Llanfabon to the south.

[citation needed] UCY - Union Cycliste Ystrad Mynach was founded in May 2013 by Arwel James and Gethin Smallwood.

The centre has taken its place on the land of the old Ystrad Mynach Hospital and was built in conjunction with many partners, including Heron Bros Ltd Of Northern Ireland, at a cost of around £6 million.

The facility is run by Caerphilly County Borough Council and it is hoped the local community will use the centre to create a thriving sporting culture within the region.