Charles, who is known as the Duke of Rothesay in Scotland, said at the unveiling: "It gives me enormous pride to be able to join you on this exposed hilltop to pay a small tribute of my own to all the remarkable Land Girls who did so much during the years when the country was under threat."
Their contribution was "truly remarkable", said Charles, who wore traditional Highland dress.
"There are still several hundred Land Girls left, the only problem is that it's taken nearly 70 years or something in order to ensure there was a memorial," he added.
The Prince said an "enormous debt of gratitude" was owed to Mr McLaren.
