[1] King was born in New Plymouth into a leading local family.
His brother, Truby King was a leading doctor and paediatrician, and founder of the Plunket Society.
[1] After education at William Crompton's school, he became a clerk at the mercantile and shipping company Webster Brothers, before co-founding his own stock and station agency with Robert Bauchope in 1880.
The new business, Newton King Limited, took off and expanded, becoming leading rural auctioneers and dealing in both seed and grain and in imports and exports.
Newton King died at his home, Brooklands, in 1927, survived by his wife, three sons and two daughters.