Hidden among the wooded hills northwest of the central Napa Valley town of St. Helena, Frias Family Vineyard is a small hand-tended property with variable terrain, from terraces to steep hillsides. The Spring Mountain appellation lies on the eastern slopes of the Mayacamas Mountains that separate Napa Valley from Sonoma Valley. Parent material for the soils are derived from weathered volcanic and sedimentary rock, and those shallow red soils are scattered with rocky debris that allow good drainage and limit the vine growth and yield. Such diversity requires careful hand work, and the vineyard is divided into multiple small plots. Yet they all contribute to the complexity of the wines grown on the estate.