Duncan arrived in Albany by ship, the Zilandia, with his mother and siblings and went by train to Katanning. In 1917 they moved to commence farming at Kojonup on approximately 628 acres where his father grew wheat then developed his own piggery. Duncan schooled at Katanning then Kojonup. His mother made butter from milk from their cows and sold to local shops.
Duncan worked for neighbours from eight years of age cutting wool bags then later sewing them when he was 17. He started shearing at 15 years of age and at 16 won the Under 21 years Great Southern Shearing Competition. He took up shearing professionally at 20 and talks about the difference between mechanical and blade shearing.
In 1925 he went to Northam to learn how to shear with machines. In 1929 Duncan went to the Kimberleys shearing and he recalls the 1930 shearers’ strike. Shearing was his main source of income until 1939 when he married and went to live at Boyup Brook.
He opened a hairdressing salon (his brother, Ron, was hairdresser) with rural agencies in 1939 and closed it in 1946 when his brother died. Duncan started farming at Boyanup from 1940 to 1974 running sheep and growing flax and other grains. He bought 520 acres on Mayanup Road, then another 1150 acre property at Dinninup Hill in 1966. Their son, Ian, came to work on the property then bought one of his own.
The Muirs sold the farm in 1974 and retired to Augusta. Duncan went fishing at Augusta, mainly in the river then in Hamelin Bay in a larger boat. He was very involved in the Mayanup Progress Association, the Royal Agricultural Society for 26 years, was Secretary of the Progress Association for three years then President and made a life member on retirement.