The McMillan Family has been practicing design and engineering since great-grandfather, William Wallace, attended lectures at the University of Glasgow, Scotland in 1844. In 1856, William Wallace came to the California Gold Fields where he operated the Phoenix Gold Mine and provided engineering services to fellow miners for 30 years.

His son, John Gilmore McMillan, practiced civil engineering in the Santa Clara Valley where he was county Engineer for Santa Clara County around 1902. He also was Leland Stanford's engineer in the early stages of the development of the 8000 acre Stanford University properties. John Gilmore also designed some of the first concrete arch bridges on the West Coast of North America.

John Gilmore's son, Percy W. McMillan took over the family surveying business after John Gilmore's retirement and did much surveying in the Valley and surrounding hills until the 1970s. His brother, William Bruce, graduated from Stanford University in 1911 and began a long career composed mostly of the design and construction of the hydroelectric facilities in the Sierra Nevada. He was the Chief Surveyor for the Hetch Hetchy gravity aqueduct still supplying water to the San Francisco Peninsula and was Chief Engineer for the road down to Big Basin Redwood State Park.

William Bruce's son, Walton Bruce McMillan continues the family business as a sole proprietor and does drafting of Civil, Structural, Planning and Architectural works.

Walton began his career after receiving a Master of Science degree in structural mechanics from San Jose State College in 1968. His first work was in the offshore petroleum industry for G. H. Pomeroy and for Earl and Wright, Consulting Engineers. He was a senior engineer for two multi-billion dollar projects in the North Sea and Northwest Australia. He was then engaged by the Lockheed Corporation in Sunnyvale, California designing and constructing marine equipment and aerospace support equipment for the Space Shuttle and for the Titan IV program, America's premier heavy-orbital launch system. Subsequently, he returned to the area of port facilities on Puget Sound, Washington state, where he was a senior engineer for the design and construction of two signature projects on the Seattle Waterfront.

Walton worked for 3 years drafting in the area of tilt-up buildings and seismic retrofit. During this time he has also earned experience in site planning, architectural and civil drafting. In the last 5 years he has been drafting residences with some work in public buildings, including schools.