Brassfield, who grew up in Porterville, California on an alfalfa farm, founded GNLD, a vitamin and nutrition supplement company.

[1] In 1973, he acquired 1,600 acres (650 ha) in the High Valley region of Lake County, California, which he expanded through successive acquisitions, totaling about 5,000 acres (2,000 ha) which include the dormant Round Mountain volcano which created High Valley.

As of 2023, the winery had approximately 500 acres (200 ha) under vines, a 1,000-acre nature preserve, and a mile-long network of caves.

[3] In addition to single varietal wines from Cabernet Sauvignon, Grenache, Malbec, Merlot, Petite Sirah, Pinot gris, Sauvignon blanc, Petit Verdot, Viognier or Zinfandel, Brassfield produces two signature blends: their red Eruption, a mix of Cabernet Sauvignon, Syrah, Malbec, Petite Sirah, Mourvèdre, Grenache and Zinfandel from their Volcano Ridge vineyard; and Serenity, a white blend of Pinot gris, Sauvignon blanc, Viognier and Gewürztraminer grown in gravelly valley soils.

The company was a key petitioner in getting High Valley recognized as an American Viticultural Area in eastern Lake County in 2005.