The peninsula was a cantref within the medieval kingdom of Gwynedd, and became part of Caernarfonshire from 1284 until that county was abolished for administrative purposes in 1974.
This perceived remoteness from urban life has lent the area an unspoilt image which has made Llŷn a popular destination for both tourists and holiday home owners.
From the 1970s to the 1990s, a group known as Meibion Glyndŵr claimed responsibility for several hundred arson attacks on holiday homes using incendiary devices, some of which took place in Llŷn.
He is credited with having sponsored Saint Cadfan's monastery on Bardsey Island, which became a major centre of pilgrimage during medieval times.
The granite quarries of northern Llŷn have left a legacy of inclines and export docks and were the reason for the growth of villages such as Llithfaen and Trefor.
Shipbuilding was important at Nefyn, Aberdaron, Abersoch and Llanaelhaearn, although the industry collapsed after the introduction of steel ships from 1880.
From the 1950s onwards, extensive use was made of artificial fertilizers, herbicides and pesticides, leading to drastic changes in the appearance of the landscape.
As car ownership increased, the tourist industry spread to the countryside and to coastal villages such as Aberdaron, Abersoch, Llanbedrog and Nefyn, where many families supplemented their income by letting out rooms and houses.
[5] During the Middle Ages the cantref of Llŷn was divided into 3 cymydau, those being Dinllaen, Cafflogion and Cymydmaen, with their respective capitals at Din Llaen, Denio and Neigwl.
Numerous granite intrusions and outcrops of rhyolite form prominent hills such as Yr Eifl, whilst gabbro is found at the west end of Porth Neigwl.
In 1984 there was an earthquake beneath the peninsula, which measured 5.4 on the Richter scale and was felt in many parts of Ireland and western Britain.
The Llŷn Coastal Path, a long distance footpath, enables walkers to fully explore both coasts of the peninsula.
[11] By 2003, however, a survey of schools showed that just over 94 per cent of children between the ages of 3 and 15 were able to speak Welsh, making Llŷn one of the foremost heartlands of the language, although, as in the rest of North West Wales, many people are concerned that the influx of English speakers is damaging the standing of Welsh and threatening its future as a living community language in the area.
Concern for the Welsh language was ignited in 1936 when the United Kingdom government settled on establishing a bombing school at Penyberth on the peninsula.
[13] The government had settled on Llŷn as the site for its new bombing school after similar locations in Northumberland and Dorset were met with protests.
[14] However, British Prime Minister Stanley Baldwin refused to hear the case against the bombing school in Wales, despite a deputation representing half a million Welsh protesters.
Protest against the bombing school was summed up by Saunders Lewis when he wrote that the British government was intent upon turning one of the "essential homes of Welsh culture, idiom, and literature" into a place for promoting a barbaric method of warfare.
The "Three" were sentenced to nine months imprisonment in Wormwood Scrubs, and on their release they were greeted as heroes by 15,000 people at a pavilion in Caernarfon.