[2] Some records claim that Milligan emigrated to Western Australia with his wife on James Stirling's expedition arriving aboard HMS Sulphur on 8 June 1829.
[2] Others claim that he emigrated to Western Australia with his wife, child and a nephew, arriving aboard Wanstead on 30 January 1830.
[2] He was the original owner of the land at the southern end of Milligan Street, Perth, which was named after him.
In 1837 Milligan published a paper in the Madras Journal of Literature and Science titled "Some Account of the New Colony of Western Australia".
[7] Milligan retired from the army in 1847 due to ill health, and lived in Nuneaton, England.