Porthmadog came into existence after William Madocks built a sea wall, the Cob, between 1808 and 1811, to reclaim a large proportion of Traeth Mawr from the sea for agricultural use.
The diversion of the Afon Glaslyn caused it to scour out a new natural harbour which had a deep enough draught for small ocean-going sailing ships, and the first public wharves were built in 1825.
Individual quarry companies followed, building a series of wharves along the shore almost as far as Borth-y-Gest, and slate was carted from Ffestiniog down to the quays along the Afon Dwyryd, then boated to Porthmadog for transfer to seagoing vessels.

In the second half of the 19th-century Porthmadog was a flourishing port, its population expanding from 885 in 1821 to over 3,000 by 1861.
The rapidly expanding cities of England needed high quality roofing slate, which was transported to the new port by tramway from the quarries in Ffestiniog and Llanfrothen.
The Ffestiniog Railway opened in 1836, followed by the Croesor Tramway in 1864 and the Gorseddau Tramway in 1856, and by 1873 over 116,000 tons (117,800 t) were exported through Porthmadog in more than a thousand ships.

A number of shipbuilders were active at this time, and were particularly well known for the three-masted schooners known as Western Ocean Yachts, the last of which was built in 1913.

By 1841 the trackway across the reclaimed land had been straightened and was to be developed as Stryd Fawr, the main commercial street of the town.
Along this street were a range of shops and public houses and a post office, with the open green retained.
A mineral railway to Tremadog ran along what was to become Heol Madog.
To the north was an industrial area where foundries, timber saw mills, slate works, a flour mill, a soda-pop plant and gasworks were constructed.

Porthmadog's role as a commercial port, already reduced by the opening of the Aberystwith and Welsh Coast Railway in 1867, was effectively ended by the First World War, when the lucrative German market for slate collapsed.
The 19th-century wharves survive, but the slate warehouses have been replaced by holiday apartments and the harbour is used by leisure yachts.

The earliest documented references to the name "Port Madoc" are from the 1830s, coinciding with the opening of the Ffestiniog Railway and the subsequent growth of the town.
The first Ordnance Survey map to use the name was published in 1838.
Its derives from the town's founder William Madocks, despite a belief that it is named after the folklore character Madog ab Owain Gwynedd, who also gives his name to "Ynys Fadog" (English: "Madog island").
The town was officially called "Portmadoc" until 1974, when it was renamed with the Welsh spelling.
Porthmadog came into existence after William Madocks built a sea wall, the Cob, between 1808 and 1811, to reclaim a large proportion of Traeth Mawr from the sea for agricultural use. The diversion of the Afon Glaslyn caused it to scour out a new natural harbour which had a deep enough draught for small ocean-going sailing ships, and the first public wharves were built in 1825. Individual quarry companies followed, building a series of wharves along the shore almost as far as Borth-y-Gest, and slate was carted from Ffestiniog down to the quays along the Afon Dwyryd, then boated to Porthmadog for transfer to seagoing vessels.
In the second half of the 19th-century Porthmadog was a flourishing port, its population expanding from 885 in 1821 to over 3,000 by 1861. The rapidly expanding cities of England needed high quality roofing slate, which was transported to the new port by tramway from the quarries in Ffestiniog and Llanfrothen. The Ffestiniog Railway opened in 1836, followed by the Croesor Tramway in 1864 and the Gorseddau Tramway in 1856, and by 1873 over 116,000 tons (117,800 t) were exported through Porthmadog in more than a thousand ships.
A number of shipbuilders were active at this time, and were particularly well known for the three-masted schooners known as Western Ocean Yachts, the last of which was built in 1913.
By 1841 the trackway across the reclaimed land had been straightened and was to be developed as Stryd Fawr, the main commercial street of the town. Along this street were a range of shops and public houses and a post office, with the open green retained. A mineral railway to Tremadog ran along what was to become Heol Madog. To the north was an industrial area where foundries, timber saw mills, slate works, a flour mill, a soda-pop plant and gasworks were constructed.
Porthmadog's role as a commercial port, already reduced by the opening of the Aberystwith and Welsh Coast Railway in 1867, was effectively ended by the First World War, when the lucrative German market for slate collapsed. The 19th-century wharves survive, but the slate warehouses have been replaced by holiday apartments and the harbour is used by leisure yachts.
The earliest documented references to the name "Port Madoc" are from the 1830s, coinciding with the opening of the Ffestiniog Railway and the subsequent growth of the town. The first Ordnance Survey map to use the name was published in 1838. Its derives from the town's founder William Madocks, despite a belief that it is named after the folklore character Madog ab Owain Gwynedd, who also gives his name to "Ynys Fadog" (English: "Madog island"). The town was officially called "Portmadoc" until 1974, when it was renamed with the Welsh spelling.
Porthmadog