The town is close to the mouth of the River Dwyryd on the A487 nearly 3 miles (4.8 km) east of Porthmadog, and had a population of 2,150 at the 2011 census,[1] increased from 2,031 in 2001.

The present town owes its existence as a commercial centre to a local landowner, David Williams of Castell Deudraeth near Minffordd, who in the mid-19th century drained the swamp and dried the pool and constructed many streets.

Adopting a scheme of town planning evolved by the builder of Tremadog and his Italian craftsmen, Williams gave Penrhyndeudraeth broad streets and wide open spaces.

[3][4] Prior to the many 19th century land reclamation projects (including The Cob at Porthmadog) and the building of the Ffestiniog Railway, both of which spurred economic growth, the few local inhabitants relied on agriculture and small-scale copper mining.

There is a history of revivalists such as Daniel Rowland who held meetings at Tyddyn Isaf and the poet Dafydd Siôn Siâms who publicly cursed the new religion before himself being converted.

Historically, the population depended on employment offered by the slate industry at Blaenau Ffestiniog and the trade in raw materials through the busy harbour at Porthmadog.

[9] On his train journey back from Essex to Durham, Cooke came across a newspaper advertisement listing government owned factories that were up for sale following the war.

HM Factory Penrhyndeudraeth drew his eye immediately and Cooke decided to visit the site and found it was perfect for the production of Nitroglycerin due to it being located in a series of valleys.

Such was the site's success, R.T. Cooke expanded the factory and subsequently decided to move the Miner’s Safety Explosives Company from Essex, to Penrhyndeudraeth.

[9] The four workers killed in the blast were named as Elizabeth Catherine Lloyd, Annie Owen, Laura Williams, and Eric Evans.

ICI's priority following its full acquisition of Cooke's Explosives was to introduce safer methods of working and heavily investing in modern technology, leading to some automation and remote control of production processes, with the aim of preventing another catastrophic accident that had blighted the factory over the decades.

[13] The prolonged miners' strike of 1984 and the competition from foreign coal imports resulted in wholesale pit closures which, in turn, reduced the demand for mining explosives to the point where production was no longer economic and the site was finally closed in 1995 and cleared in 1997, bringing nearly 130 years of explosives production at the site to an end.

[10] The nature reserve is officially known as “Gwaith Powdwr” (Powder Works) a befitting homage to its explosive industrial past, ensuring its continued place firmly in the history books.

Another 19th-century industry in the district is Garth Quarry at Minffordd, established in 1870 to make granite setts for road building in towns and cities.

For generations, the Grade II listed Pont Briwet carried the Cambrian Coast Railway, allowing people to cross Afon Dwyryd from Penrhyndeudraeth to Llandecwyn along a narrow road suitable for cars only.

According to the 2011 Census, Penrhyndeudraeth is the 19th most Welsh-speaking community in Wales, with approximately 76% of its residents aged three years or older stating that they could speak Welsh.

[14] According to the latest Estyn inspection report of the village's primary school, Ysgol Cefn Coch, 79% of pupils come from homes where Welsh is spoken.

Penrhyndeudraeth's Alun 'Sbardun' Huws wrote a song, Strydoedd Aberstalwm (approximately "streets of long ago"), in tribute to the village.