- 1067 Chepstow Castle was the first stone castle to be built in the area covered by modern-day Britain. Built by the Normans, the Great Tower keep dates from 1067, one year after the Norman conquest.
- 1170 First discovery of America. The first European to visit America was Prince Madog, who sailed from Ynys Fadog, near present-day Porthmadog, to North America in 1170. ( Porthmadog and Tremadog were founded in the nineteenth century by William Alexander Madocks, and apparently the names of the towns have a nice "double origin" referring to both Madocks and Prince Madog ).
- The first use of the skull and crossbones was reputedly by the Welsh pirate Bartholomew Roberts (Black Bat, Baiti Ddu) pirate.
- 1775 The stone bridge in Pontypridd was built in 1775 and was once the longest single-span stone bridge in the world. Built by William Edwards,who had made previous attempts which had collapsed into the River Taff.
- 1794 Crawshay buys the Cyfartha iron works. At the end of his life he has become one of Britain's first millionaires.
- 1804 The World's first steam locomotive ran for 15 and a half kilometers between Penydarren, Merthyr Tydfil and Abercynon, carrying 10 tons of iron and 70 passengers, at 8 kph.
- 1807 The world's first fare-paying passenger railway, the horse-drawn Oystermouth and Mumbles Railway.
- 1826 The Menai Bridge becomes the first major suspension bridge.
- 1865 A successful Welsh colony established at Chubert, Patagonia and claimed to be the first community to give the vote to women.
- 1882 First lager to be brewed in Britain, in Wrecsam (Wrexham). Brewing ceased when Carlsberg took them over. (Licensed to Thwaites of Lancashire???). There is a possibility that brewing will re-start in Wrexham.
- 1896 Lake Vyrnwy was created by use of the first major masonry dam. This lake provides water to Liverpool.
- 1897 On 11. May 1897, Marconi transmitted sound from Lavernock Point, south of Penarth near Cardiff to his assistant, George Kemp, on the island of Flat Holm, five kilometers away - the first time a signal had been sent across water. . His first words were apparently :"Are you ready", the incident is recorded on a plaque on the wall of an adjacent Victorian chapel.
- First Flight
1900 the Welsh constituency of Merthyr Tydfil returned Britain's first Labour MP - Kier Hardie. 
- 1905 Adelina Patti, world-famous Spanish opera singer but resident in Craig-y-Nos Castle on the A4067 between Ystradgynlais and Sennybridge, made a gramophone record whch is believed to be the first recording of a prima donna's voice. It was recorded at Craig-y-Nos itself.
- 1915 The Women's Institute is set up in Llanfairpwll.
- 1921 Morgan Jones is elected MP for Caerffili - the first concientious objector to become an MP.
- 1922 First Communist candidate at a British election, at a by-election in Caerffili.
- 1927 Malcolm Campbell achieved a world land speed record of 174.88 mph on Pendine Sands. An attempt, at the same location a few weeks later, to better this by the Welshman J.G. Parry-Thomas ended in tragedy when he was killed.
- First Youth Hostel in Britain - Pennant Hall, Conway Valley
- 1933 Lionel Brabazon Rees set sail from Caernarfon in 1933 in a 34 foot ketch and sailed to Miami, the first single-handed crossing of the Atlantic.
- 1935 The Felinfoel Brewery, Llanelli were the first brewery in Europe to sell beer in cans. They were just beaten to it by the Americans.
- 1945 In the Neath by-election, the first "Trotskyist" candidate in a British election.
- 1949 First comprehensive school south of Scotland, at Holyhead.
- 1950 first scheduled helicopter service - between Cardiff, Wrexham and Liverpool.
- 1957 Anglesey become the first Local Education Authority to abolish the 11-plus.
- 1962 World's first hovercraft service between Rhyl and Wallasey
- 1962 World's first hovercraft wreck, off Rhyl.
- 1982 Wales became the first nuclear-free country in Europe when all the counties agreed not to allow nuclear weapons on their soil.
