To mark the event, the Oxfordshire UNESCO World Heritage Site is asking visitors and former members of staff to send in images and reminisces about their experiences over the last seven decades.
Dominic Hare, chief executive officer at Blenheim, said: “This beautiful and historic site holds a special place in many people’s memories and we would love to be able those stories and reminisces into the wider history of the Palace itself.
“Our guides often hear from visitors who remember being brought by their parents and grandparents and who are now returning with their own children and grandchildren.
“We are also very keen to hear from former members of staff and those who have worked on the Estate over the years.
“Some aspects of the visitor experience have changed out of all recognition, while others remain virtually identical to that first day back in 1950.
He added: “Hopefully we will be able to piece together a tapestry of words and pictures representing every decade we have been open to form a fascinating overview of the development of a visitor attraction over time."
‘Britain’s Greatest Palace’ officially first opened its doors to the public on 1st April 1950 with visitors paying half a crown admission.
It proved to be extremely popular with the 10th Duke of Marlborough recalling about 5,000 people visited over the first time weeks with no fewer than 2,400 paying guests alone on Easter Monday.
In total it is estimated around 100,000 came to see the Palace in its first year. By contrast Blenheim Palace welcomed more than 920,000 visitors in 2019.
People can share their stories of either visiting or working at Blenheim Palace by visiting www.blenheimpalace.com/70years where they can upload up to 10 images along with information on their visit.