Trevor McMillan began his career as a skilled and efficient blacksmith and engineer in 1947 in the village of Southbridge, Canterbury. This included well drilling within the Canterbury Plains.

Family succession instigated the expansion to independently-owned companies for different areas of the business. Lyell and Val began the drilling facet as a drilling company, starting with five rigs and six staff.

Until the 1980s, the plains of Canterbury were only considered good for shallow irrigation or domestic water bores. The company researched a new style of rig that could drill much deeper and faster, resulting in the first Rotary Drill Rig arriving in the country in 1982. The months that followed were spent customising the equipment to suit the local conditions.

While the construction of water supply wells formed the backbone of the company, the business continued to grow and diversify into markets such as minerals, geotechnical/environmental, geothermal and civil. Value-added services also included the introduction of a fully accredited laboratory for the testing of water quality.

Operations continued to expand geographically and McMillan Drilling responded by establishing businesses in Fiji and Auckland.