The Southern Hemisphere's biggest necropolis is bursting at the seams

Robyn Hawes was trying to save the memory of thousands of graves at Sydney's Rookwood Cemetery when she stumbled unknowingly on the names of her own relatives.

In 1981, Ms Hawes, with the Society of Australian Genealogists, moved to transcribe 750,000 graves at Rookwood after a road project had removed a swathe of headstones, resulting in four sections being effectively lost to history.

She said the society was worried that more of the cemetery, which had no heritage listing, might meet a similar fate.

"We expected that maybe that would all be demolished and built over with units or whatever," Ms Hawes said.

Ms Hawes looked up one day while transcribing to see names she recognised — Edward and Sarah McCamley, her great-grandparents who had come to Australia from Ireland in the 1850s.

"I knew they were my great-grandparents, but I didn't know very much about them," Ms Hawes said.

Ms Hawes is the president of the Friends of Rookwood group, which runs tours at the cemetery and raises money for restorations for the older parts of the cemetery.

It took eight years to transcribe all the graves at Rookwood. At the same time, in 1989, the Heritage Council of NSW placed a permanent conservation order on the cemetery, and 10 years later it was upgraded to the State Heritage Register.

Founded in 1867 on 80 hectares in an area formerly known as Haslams Creek, the cemetery popped up as Sydney was growing and the original cemetery at Devonshire Street, where Central Station is now, was getting full.

It was once serviced by a train link from Central twice a day on the so-called mortuary line, which had three stops inside the cemetery.

From the beginning, the cemetery was divided up into six denominations: Anglican, Catholic, Presbyterian, Wesleyan, Independent and Jewish.

Since then, the cemetery has grown to facilitate graves for 140 religions and 250 different languages.

Metropolitan Memorial Parks (MMP) manages 190 hectares of Rookwood, which is about two-thirds of the cemetery, while Catholic Cemeteries and Crematoria manages the other third.

The cemetery will celebrate its 159-year history on Sunday this weekend with a heritage day festival that includes a grave-digging demonstration and tours of the graves of famous Australians including suffrage pioneer Louisa Lawson, retailer David Jones and biscuit maker William Arnott.