The village grew around the local slate industry with many houses being built to house quarry workers and their families. The village is renowned for a street of houses that were built by Lord Penrhyn, proprietor of the Penrhyn Quarry and occupier of Penrhyn Castle to accommodate the workers that refused to strike during the Penrhyn Lockout of 1900-1903. The street, Tanrhiw Road, was known locally as 'Stryd y Gynffon' (Traitor's Row or Tail Terrace) and was one of the first main settlements in the village based alongside the farmsteads of Ty'n Clawdd, Tanrhiw Isaf and Tahrhiw Uchaf.
The village is the birthplace of a number of local luminaries such as the late Sir Ifor Williams, the late Ifor Bowen Griffith, the late T. Gwynn Jones  and actor John Ogwen. Tregarth is also home to sculptor Ann Catrin Evans.
Tregarth has its own primary school, chapel (Shiloh), parish church (Santes Fair, St Mary's) and community centre which is the venue for many village activities such as Ysgol Feithrin (nursery school), Youth Club, Clwb yr Henoed (Senior Citizens Club) and Snooker Club. The public house, Pant yr Ardd, was closed and put up for sale in June 2014. It was bought by an unknown source and is re-opening on the 5th of December 2014.
Owing to Bethesda's industrial heritage, Tregarth has two railway lines running through its centre, one The Bethesda Branch (London and North Western Railway) which was closed in 1963 and the other The Narrow Gauge Penrhyn Quarry Railway Line which was used to transport slate from the Penrhyn Quarries to Port Penrhyn and was closed in 1962. These lines have since been converted to cycle paths as part of Sustrans Lôn Las Cymru cycle route 5 and take the cyclist on a journey from the Nant Ffrancon Pass winding through Tregarth down along the River Cegin towards Bangor and Port Penrhyn. An hourly bus service into the town is provided by both Arriva Buses Wales and Padarn Bus.
The Moelyci Environmental Centre (Canolfan Amgylcheddol Moelyci) can also be found in Tregarth which is a community based centre that specialises in the practice and teaching of sustainability. The centre runs many open days and activities and welcomes visitors.
- The Great Strike 1900-03
- Obituary -T Gwynn Jonesl
- Prichard, Alun (December 20, 2002). "Ann's career is forging ahead; The North Wales designer who is proving a hit in Europe's top crafts show". Daily Post.
- "cobr.co.uk". cobr.co.uk. Retrieved 2013-05-23.
- Moelyci Environmental Centre (Canolfan Amgylcheddol Moelyci)