Born in Alma in the Mid North of South Australia, he was educated at Winham College before becoming a farmer at Dalkey near where he grew up.

[1] McLachlan married Ellen Louisa Jury in 1894 and abandoned farming in 1902 following a severe drought.

After working as a storekeeper and agent, he was elected to the South Australian House of Assembly as the Liberal member for Wooroora in 1918, serving until 1930.

He resigned on 31 January 1930 to take up an appointment on the Pastoral Board of South Australia.

[3] McLachlan held his seat until his retirement in 1946 (by which time he was a member of the Liberal Party).