[2] Mills was a surveyor on George Goyder's mission to survey a northern capital Palmerston, later renamed Darwin.

He arrived on the Moonta on 5 February 1869 leaving just short of a year later, the team having surveyed more than 2700 square kilometres of land.

[2] On 5 September 1870, he joined Charles Todd's party to build the central section of the Overland Telegraph Line.

[5][6][1] After completion of the telegraph line, Mills returned to the Northern Territory to work in mining and undertake further surveying.

[7][8][9][10] In the early 1880s, he managed a camel transport company carrying freight from Farina to Peake and Charlotte Waters.