While city-based, much of her inspiration came from her brother's farm at Gunnedah in northern New South Wales. Mackellar's most famous poem, "My Country", was first published in 1908 in the London Spectator under the title "Core of My Heart", when the author was only 19. Taught to generations of Australian school children, this poem declares the author's love not for England, but for a land of extremes, a brown and pitiless country of droughts and flooding rains.