The public building, at the time of its completion, was the tallest storeyed building in Ireland at 64.3m high.
It retained that status until 2008 when surpassed by another Cork development, the city centre residential and retail complex, The Elysian.
County Hall was completed in 1968, and its construction will be celebrated on April 16.
The headquarters of Cork County Council, the original 16-storey building was designed by the council’s county architect Patrick McSweeney. It has since been further enhanced.
In recognition of the anniversary, an exhibition will go on display on April 16 at 1pm in the foyer of the building, providing the story of the County Hall structure from inception to completion.
Mayor of the County of Cork, Declan Hurley, together with chief executive of Cork County Council, Tim Lucey, will unveil a commemorative plaque.
Mr Hurley has asked Cork people to visit County Hall on the occasion and experience the magnificence of the building.
“County Hall has become synonymous with Cork,” he said.
It is a building Cork is proud of and one which resonates with the people of Cork.
“It has always been a landmark building.”
The high-rise solution was a striking architectural concept in the 1960s which had not been attempted previously in Ireland.
When completed in 1968, the design was a single, elegantly proportioned, vertical block with a textured surface of precast concrete tracery which eliminated the need for scaffolding during construction.
This distinctive white concrete tracery formed a latticework over the building. It concealed the platforms outside the windows, on which each floor was created.
A redevelopment project began in 2002, as the original concrete facade had been severely eroded and the panels were replaced as part of an expansion scheme. An extra storey extended the building’s height to 67m with a glazed pavilion offering panoramic views of Cork city and environs.
Mr Lucey noted the impact of the building on Cork.
“In 1968 at the official opening, then county manager Michael Conlon noted this County Hall belonged to the people of Cork,” he said.
It continues to belong to the people of Cork and will continue to be a building which delivers for the people of Cork.