1925: Plaid Cymru formed
1966: Plaid Cymru won its first seat in Carmarthen.
1970: Plaid Cymru fielded a candidate in every seat in Wales in the election and got 11.5% of the vote in Wales.
1974: (Feb) Plaid Cymru won 2 seats to Westminster. In the October election, Plaid Cymru won 3 seats in total.
1979: the devolution referendum failed in Wales. Only 12% of the possible electorate supported devolution – well below the 40% needed to proceed. Only 59% of those who could have voted did so in Wales that was far lower than in Scotland. In the election of this year, Plaid Cymru lost one MP and its share of votes fell to only 8%.
1987: Plaid Cymru's support at the election fell to 7.3% but won 3 seats to Westminster.
1997: only 50% of potential voters turned out for the 1997 referendum on a Welsh Assembly and it was voted for by a very small majority.
1999: Plaid Cymru won 17 seats to the National Assembly of Wales out of a possible 60 seats – the second largest party in the Welsh Assembly.
"Key Dates for Plaid Cymru". HistoryLearningSite.co.uk. 2006. Web.