Built in 1710 by the merchant and property developer Joshua Dawson, after whom Dawson Street is named. Dublin Corporation purchased the house in 1715 for assignment as the official residence of the Lord Mayor. It retains this purpose to this day.
In 1821, the Round Room was built in order to receive King George IV. while the distinctive metal portico over the main door was erected for the visit of Queen Victoria in 1900. The First Dáil assembled in the Round Room on 21 January 1919 to proclaim the Irish Declaration of Independence. In 1921, the Anglo-Irish Treaty was ratified in the same location.