N. John Hansen began his work for the Extension Service in 1943 in Linn County with responsibility for the county's 4-H program. From 1949 until 1972, he acted as Staff Chair in Polk County. Hansen served as an area water resource specialist in Salem for 18 months prior to his retirement at the end of 1973. While serving as said specialist, he assisted in the development and organization of four Rural Domestic Water Systems that today serve the majority of rural Polk County.
In 1963, Hansen, along with the 20-40 Club, a group of young farmers and WWII veterans, received national recognition for the work they had been doing in implementing an annual soil testing program for local farms, beginning eight years previous. Their story, as well as a cover picture, was featured in a 1963 issue of "Agricultural Leaders' Digest."
During his employment at Extension, Hansen also worked in the offices of the National Association of County Agricultural Agents. He was appointed Chairman of the Professional Training Committee in 1962, and elected Vice-President of the NACAA in 1964. In 1966 he represented, on a national level, all County Agricultural Extension Agents in a meeting between the U.S. and Japan that helped pave the way for agricultural trade relations between the two nations.
After his retirement, Hansen remained active in the agricultural community, working with the local chapter of 4-H, the Oregon Milk Stabilization Program, the Oregon Soil & Water Conservation Commission and the Oregon Coordinated Resource Management Program, and guiding agricultural studies tours, alongside his wife, in a number of foreign nations.