On 6 January 1818, the new post-office in Sackville Street (now O'Connell Street) was opened for business... the building,...is built after a design of Francis Johnston,... The structure was completed in the short space of three years for the sum of £50,000

During the Easter Rising of 1916, the GPO served as the headquarters of the uprising's leaders. The assault by the British forces extensively damaged the building and it was not repaired until the Irish Free State government took up the task some years later. The original columns outside are still pocked with bullet-marks.[3][4] An original copy of the Proclamation of the Irish Republic is on display in the An Post museum at the GPO, where an exhibition highlights the history of the postal service and the GPO. The building has remained a symbol of Irish nationalism. In commemoration of the Rising, a statue depicting the death of the mythical hero Cúchulainn sculpted by Oliver Sheppard in 1911 is housed in the front of the building and was featured on the Irish ten shilling coin of 1966. Despite its fame as an iconic place of Irish freedom, ground rent continued to be paid to English and American landlords until the 1980s.[5]

The broadcasting studios of 2RN, which later became Radio Éireann, were located at the GPO from 1928 until the 1960s.[6] Draws for Prize Bonds are held weekly, on Fridays, in the building. Source - Wikipedia