A census, which shows where people lived, their age, place of birth and occupation, is taken once a decade but then not released to the public for a century.
With the 1931 census lost to fire, the 1921 census has taken on even greater importance.
Barnsley’s Family History Society’s general secretary Margaret Williams shares the nationwide excitement.
She said: “The 1921 census was taken at a time of massive change.
“Thirty million people are recorded but due to the First World War, there are a huge number of fatherless children.
“There is also the changing role of women (who had been given the right to vote three years earlier) and also the effects of the Spanish flu.
“It was also the first time that people could answer yes or no to being divorced.
“It’s a real crossroads in history.”
Family historians can now also tangibly get closer to relatives they knew.
Margaret said it is important to not take everything as gospel.
She added: “It’s the first time that some people will get to see their grandparents on a census, which is exciting.
“People are interested in their family trees but often don’t know how to go about it.
“Write down what you know, ask elderly relatives and take it from there on one of the genealogy websites.
“The documents can then verify what you know.”
People interested in delving into their family history can get more information from the society’s website: www.barnsleyfhs.co.uk