Sinn Féin's elected representatives meet in Dublin’s Mansion House to declare a republic and form the first Dáil Éireann. The Dáil approves a provisional constitution and issues a Declaration of Independence, a message to the Free Nations of the World, and a Democratic Programme.
Two members of the Royal Irish Constabulary (RIC) are shot dead during an ambush by members of the 3rd Tipperary Brigade, Irish Volunteers. The attack, which is carried out without the authorisation of the Dáil or Volunteer General Headquarters, is considered by historians as the starting point of the War of Independence.
Dáil Éireann confirms the policy of peaceful boycott against the RIC initiated by republicans in 1917.
Laurence Ginnell, who was elected as Westmeath's representative in the 1918 general election, is arrested by the police in Dublin. He is subsequently sentenced to four months in prison.
The RIC baton charge a large crowd in Castlepollard. The crowd had gathered to hear a speech by Hanna Sheehy Skeffington. Other towns in Westmeath witness similar scenes during the summer of 1919.
In Mullingar, a vast street brawl occurs between British soldiers and local men.
Volunteers take an oath of allegiance to the Republic and begin using the name Irish Republican Army (IRA).
The British government declares Dáil Éireann an illegal assembly. Other organisations, such as Sinn Féin, Cumann na mBan and the Gaelic League, are also declared illegal before the end of 1919.