Catherine Corless has been examining child death records at the Catholic nun-run home in Tuam, County Galway.
Church leaders in western Ireland said they had no idea so many children who died at the orphanage had been buried in the grave and they would support local efforts to mark the spot with a plaque listing all 796 children.
County Galway death records showed that the children, mostly babies and toddlers, died often of sickness or disease in the orphanage during the 35 years it operated from 1925 to 1961. The building, which had previously been a workhouse for homeless adults, was torn down decades ago to make way for new houses.
A 1944 government inspection recorded evidence of malnutrition among some of the 271 children then living in the Tuam orphanage alongside 61 unwed mothers.
The death records cite sicknesses, diseases, deformities and premature births as causes. This would reflect an Ireland that, in the first half of the 20th century, had one of the worst infant mortality rates in Europe, with tuberculosis rife.
Elderly people recalled that the children attended a local school - but were segregated from other pupils - until they were adopted or placed, at around seven or eight, into church-run industrial schools that featured unpaid labour and abuse.
It is well documented that throughout Ireland in the first half of the 20th century, church-run orphanages and workhouses often buried their dead in unmarked graves and unconsecrated ground, reflecting how unmarried mothers - derided as "fallen women" in the culture of the day - were typically ostracised by society, even their own families.
Tuam locals discovered the bone repository in 1975 as cement covering a buried septic tank was broken away. Before Ms Corless' research this year, they believed the remains were mostly victims of the mid-19th century famine that decimated the population of western Ireland.
Finbar McCormick, a professor of geography at Queen's University Belfast, said the children's last resting place would not have been the septic tank itself. He added: "The structure as described is much more likely to be a shaft burial vault, a common method of burial used in the recent past and still used today in many parts of Europe."
Respectful of the unmarked grave in their midst, residents have long kept the grass trimmed and built a small grotto with a statue of the Virgin Mary.
Archbishop of Tuam Michael Neary said he would meet leaders of the religious order that ran the orphanage, the Bon Secours Sisters, to organise fund-raising for a plaque listing the 796 names and to hold a memorial service there.
Ms Corless and other Tuam activists have organised a Children's Home Graveyard Committee that wants not just a lasting monument to the dead, but a state-funded investigation and excavation of the site.
The government has declined to comment. Ireland has already published four major investigations into child abuse and its cover-up in Catholic parishes and a network of children's industrial schools, the last of which closed in the 1990s.
29.8.14 Editor's note: this online-only article was supplied by the Associated Press agency to HeraldScotland and published in good faith. In light of a subsequent correction issued by the agency, we have edited the above article and reproduce the correction in full below:
In stories published June 3 and June 8 about young children buried in unmarked graves after dying at a former Irish orphanage for the children of unwed mothers, the Associated Press incorrectly reported that the children had not received Roman Catholic baptisms; documents show that many children at the orphanage were baptised.
The AP also incorrectly reported that Catholic teaching at the time was to deny baptism and Christian burial to the children of unwed mothers; although that may have occurred in practice at times, it was not church teaching.
In addition, in the June 3 story, the AP quoted a researcher who said she believed that most of the remains of children who died there were interred in a disused septic tank; the researcher has since clarified that without excavation and forensic analysis it is impossible to know how many sets of remains the tank contains, if any.
The June 3 story also contained an incorrect reference to the year that the orphanage opened; it was 1925, not 1926.