In 1978, Randy and Lori acquired a 14-acre parcel in Angwin, which included approximately 5 acres of Cabernet vines. At that time, Randy was employed full-time as a winemaker in Rutherford. During evenings and weekends, Randy, Lori, and their young son Mike cared for the vines. In the same year, Randy also took on the responsibility of farming and purchasing fruit from Harry Frank's adjacent property. The initial harvest from these two vineyards produced 9 tons of fruit. Randy further acquired an additional 3 tons from Beatty Ranch, marking the beginning of Dunn Vineyards.

The pace of development quickly accelerated. Randy, Lori, Mike, and their baby daughter Jennifer moved onto the property that would later become the winery. By 1981, the winery was officially bonded. In 1984, the ATF recognized Howell Mountain as a sub-AVA of Napa Valley. Kristina was born, and Lori was busy managing two young daughters and a teenage son while Randy continued to work in the valley, limiting the family’s involvement in the business to evenings and weekends. Despite these challenges, the business flourished. By 1985, the family moved into a new home, known as the "Brown House," and Randy left his valley job.

By the end of the 1980s, Dunn Vineyards had become a thriving enterprise. Randy was consulting for other wineries and consistently selling out his wine. In 1989, facing a shortage of storage space for barrels, he excavated into the mountain to create additional storage, providing room for more barrels and space for Jenny and Kristina to rollerskate.

In 1999, Mike returned part-time to assist with the business. It took about three years, but he eventually joined full-time. Kristina, having graduated from Cal Poly with a degree in winemaking and viticulture, also joined the team. By 2005, both children were working full-time for Randy, marking a new chapter for the family business.

The elevation of over 1,400 feet offers several advantages, including increased sunshine and more moderate temperatures. However, spring begins later and the area is cooler than the valley floor, with frost posing a risk from bud break through flowering. In 2008, a severe frost with temperatures plummeting to 19 degrees over four days severely impacted half of the crop. Yields average about 2 tons per acre, which is relatively low, but the cool, wet vintages mitigate some of the negative effects typically experienced at lower elevations.

Today, the property is home to approximately 42 acres of Cabernet Sauvignon. This size allows for effective management of all farming and winemaking operations directly by the family.