The final three nuns from the Order of the Daughters of the Cross of Liège, which moved to Penzance in 1901 and Hayle a year later, are set to leave their convent next month.
The order says a lack of people wanting to join the religious way of life has made it necessary for it to reorganise its communities.
The Daughters of the Cross of Liège were responsible for founding St Michael's Hospital, St Julia's Hospice and Marie Thérèse House in Hayle, St Mary's Catholic School in Penzance and a number of other schools which have since closed down.
Nuns ran the hospital from its opening in 1914 until 1999 and Sisters Maureen McNally, Rose Marmion and Teresa Imelda have all lived in the Hayle convent for decades.
Sister Maureen worked as a matron at the hospital, Sister Rose was a teacher at St Mary's and Sister Imelda a minister.
John Coombe, Cornwall councillor for Hayle South, grew up in the town and said he had always admired and respected the nuns.
"They weren't just nuns and a closed order. They were involved in anything and anybody in town," he said.
"They're three people I owe an awful lot to.
"They've been absolutely tremendous and Hayle has a lot to thank them for.
"It's going to be a great loss to the town. You can't praise them too much – they were the salt of the earth."
Sisters Imelda and Rose will be moving to the order's convent in North Cheam, west London, while Sister Maureen will be joining its foundation at Haslemere in Surrey.
Sister Rose explained: "There aren't many sisters any more. We're not getting a lot of people coming so we're getting fewer and older, so we're consolidating in our bigger houses.
"I think in everybody's memories in Hayle we've always been there, so it's a big change."
The first home set up by the order in Cornwall was in Penzance at Albert House on Alma Terrace and later Leskinnick House, which also housed St Gertrude's School. The Penzance community left in 1947.
The order first moved to Hayle in 1902 and set up a house at The Downes, which is now a residential care home.
In 2002 it was decided the building was too large for their needs and they moved to St Mary's Convent, in front of the hospice on Foundry Hill.
Father Phillip Dyson, of the Penzance parish, said: "We're going to miss the three of them terribly, but at least there's a legacy in the hospital.
"These three, but also all the sisters since 1901, have been a great force for 110 years."
Churches Together in Hayle will be hosting a farewell to the sisters at the Hayle Day Care Centre at 3pm on Sunday. Everyone is welcome.