At 16 years old he began his training as an engineer in Dublin, where his abilities as a surveyor and people manager quickly became apparent.

At the age of 21 he moved to New Zealand to further his engineering career, and by 1873 he had risen to the position of Under Secretary for Public Works.

He accepted an offer for the position as Engineer-in-Chief for Western Australia in 1891 at a time when the colony was heading towards a major public works program.

O'Connor was able to convince the Government that a river mouth harbour was the best option for Fremantle. The design and construction of the harbour at Fremantle, commenced in 1892, was C.Y. O'Connor's first major public works project.

It was a huge undertaking, involving blasting to clear away the rocky bar that had, until then, blocked the entrance to the Swan River.The first stage of Fremantle Harbour Works began with a ceremony in which the Governor's wife, Lady Robinson, tilted the first truck load of rubble for the North Mole.

Dredging was required to deepen the harbour; twin breakwaters (North and South Moles) were constructed and wharves were built.

The Inner Harbour at Fremantle was officially opened on 4 May 1897.

The harbour was of great importance to the Western Australia's future prosperity.

It is testimony to O'Connor's vision that the Inner Harbour is still largely based on his original design, although the port facilities and infrastructure have been progressively modernised over the years to meet the changing requirements of shipping.

Construction and expansion of the port has continued over the years and, today, Fremantle is one of Australia's fastest growing general cargo ports.

A memorial statue honouring C.Y. O'Connor was erected on Victoria Quay on 23 June 1911 and can be seen today near the entrance to Fremantle Ports Administration Building in Cliff Street.