Agnes McWhinney wanted to be a doctor after she graduated from Townsville Grammar School. However the nearest medical school was in Sydney and was very expensive. Her brother, Joseph, worked as a solicitor at Ryan Wilson & Grose in Townsville and watching him work, Agnes developed an interest in law.

"A remarkable and strong-minded young woman with confidence in her own ability, determined to succeed."

In 1910, Ryan Wilson & Grose accepted Agnes as an articled clerk, a revolutionary step. At that time the only qualified women in law in Australia were Greta Flos Grieg, who had been admitted to practise in Victoria in 1905, and Eda Evans who had graduated from the University of Sydney in 1902 but was not permitted to practise until 1921.

On 7 December 1915, Agnes McWhinney was admitted to practise as a solicitor, the first woman in Queensland to achieve this distinction. It is possible that Agnes was the second woman to practise law in Australia, although this is not certain due to a lack of records.

Agnes continued to practise as a solicitor with the firm until 1919 when she decided to marry. Agnes was married in March 1920 and, as was the custom of the time, she gave up her work. She and her husband ran a farm near Sandgate for a number of years. Agnes died on 4 August 1985.