Lorna has lived through two world wars, two pandemics and 26 Australian prime ministers

Lorna Henstridge walks around the garden of the Bordertown Memorial Hospital, where she lives, every day. (ABC South East SA: Eugene Boisvert)

Bordertown's Lorna Henstridge will celebrate her 112th birthday on Saturday, June 6, making her Australia's oldest woman and the nation's second oldest person.

She has lived through two world wars, two pandemics, the Great Depression and 26 Australian prime ministers.

Mrs Henstridge will celebrate the milestone with family and friends at her former home in the south-eastern South Australian town of Keith.

When Lorna Henstridge (nee Paterson) was born on June 6, 1914, the nation's capital — Canberra — had been named and proclaimed for less than a year.

Australia was on the verge of sending her troops overseas as World War I broke out, and the Titanic had sunk to the bottom of the Atlantic two years earlier.

Today, Mrs Henstridge marks her 112th birthday, surrounded by family in her former home in Keith, in south-eastern South Australia.

Her eldest daughter, Jennie Jacobs said for Lorna, it was just another birthday.

"She says occasionally, 'I don't know myself how I got to be so old,"' Ms Jacobs said.

"We look at her in a totally different light than she looks at herself."

Mrs Henstridge, who now lives in Bordertown, previously told the ABC she doesn't know exactly what has been the key to her (extraordinarily) long and mostly healthy life.

Ms Henstridge was born Lorna Paterson in 1914. (Supplied: Lorna Henstridge)

The mother of three, grandmother of seven and great-grandmother of eight said she grew up in a "very different" era to today's world.

"When I was a child, we didn't have much and we didn't want for much. My father died in his 30s so my mother — who was very good to us children — had to raise us and run the farm on Yorke Peninsula on her own," she recalled.

Mrs Henstridge (then Lorna Paterson) was sent to Adelaide to begin school, where she graduated from St Peter's Girls' School with a mind for business and an A-grade hockey reputation.

She began work with a shoe importer in the city, after completing a business course.

Lorna Paterson and a friend on horseback in the 1940s. (Supplied: Lorna Henstridge)

The then Miss Paterson met her husband Alan Henstridge, and the two married before settling in Keith to run a shoe store in the town.

"We were very happy together and had three young children. Our weekends were entirely taken up with sport and it was a very good life," she said.

Mrs Henstridge played the organ in the local church for decades, and was a dab hand with a golf club and on th