He was born in Spearfish, South Dakota, and attended for two years at Princeton University, after which he dropped out in 1925 to live and travel in Europe.
Together with Baudoin, Schoonmaker played a seminal role in creating a market for wines bottled by the grower/winemaker rather than by a negotiant' – a merchant/shipper.
As a consultant to such Californian wineries as Wente and Almaden, Schoonmaker introduced the idea of labeling wines using varietal names (such as Pinot noir, Chardonnay, or Riesling) rather than semi-generic names borrowed from European regions ("Burgundy", "Chablis", "Rhine", etc.).
Robert Mondavi was one of the first to label the majority of his wines by varietal names and was tireless in promoting the practice.
This has become the standard in New World wine and some European producers are adopting the practice because of consumer demand.