He was born in Rockhill, two kilometres southwest of Bruree County Limerick, Ireland on 1 October 1843,[1] to John Sandes Cussen and Catherine Carroll.

[2] He published many research papers including early documentation of Māori people[3] and was a member of the Royal Geographical Society of Australasia.

On 17 October of the same year, at St Francis' Catholic Church, Shortland, Thames, he married Annie Wallnutt, who was also of Irish birth.

When the King Country was opened to European settlement in 1883, Cussen and his staff carried out the triangulation survey of this huge area stretching from Kihikihi to Mt Ruapehu.

Nevertheless, the survey went ahead steadily and in his reports Cussen gave detailed accounts of the country and its potential for development.

In the course of this work Cussen climbed Mts Ngauruhoe, Tongariro and Ruapehu, giving graphic descriptions of them and making observations on their geology.

Cussen, himself a member of the institute, presented papers on the geology of Mt Ruapehu, Waikato and the King Country.

He was 'uniformly courteous and high spirited, with a keen sense of honour, which guided him in his relations with his fellow men and commanded their respect and affection.'

Cussen's pioneering survey of the King Country was the essential preliminary to the development of roads, the main trunk railway and farm settlement.