[8] During the 1920s, Italian migrants primarily transformed the Templeton landscape by removing forests to farm grains and plant Zinfandel grapes in their own small vineyards.

The Paso Robles and Templeton areas are similar in geography and climate to Northern Italy with crops and vineyards planted in rolling hills and on steep mountains.

They became known for their blend of Zinfandel, Alicante Bouchet, and Carignane producing wine in their homes and wineries for religious and medicinal purposes, sold to friends and the black market.

Some were arrested, fined by local authorities, had their homes raided and barrels axed and a few spent time in jail, but their wine production still thrived.

[9] An expansion of grape growing and wine making in the region began in 1976, when Pasquale Mastan started Mastantuono Winery, which he moved a few years later to a location near Highway 46 West and Vineyard Road.

"[2] Fratelli Perata – west of Highway 101 between Paso Robles and Templeton – was established in 1989, and nearby Hope Farms Winery was founded next to already planted estate vineyards in 1990.

[2] By 1993, when The Wine Atlas of California and the Pacific Northwest by Bob Thompson was published, the book’s Paso Robles map shows six wineries and a scattering of vineyards in the Templeton Gap region.

This gap consists of several passes through the Santa Lucia Range formed by streams carving into the soft rocks of the Monterey Formation near the heads of their watersheds.

The Pacific Ocean is approximately 18 nautical miles (33 km; 21 mi) to Paso Robles from its closest point being the town of Cayucos which sits at the inner apex of Estero Bay.

These hills, located between one and four miles (two and six kilometers) east of the Salinas River, temper the further eastward, full cooling effects of the winds that flow from the southwest through the Templeton Gap; depending on the depth of the marine layer, fog often settles in this area and is the most visible reminder to local residents of the Templeton Gap viticultural area.

The passes in the crest of the Santa Lucia Range, collectively known as the Templeton Gap, bring the Pacific Ocean’s maritime influence into the viticultural area.

Also, given the sea breeze influence in the region, slope angle and aspect are important factors in determining the suitability of vineyard sites for different grape varieties.

According to the petition, the soil characteristics make low vineyard yields common within the Templeton Gap District viticultural area.

The influence of the coastal climate that flows through the Templeton Gap touches almost every district in the region, and provides a crucial feature in the growth process for the AVA.

However, vineyards in the district also produce several of the wines the Paso Robles AVA is widely known for, Syrah, Zinfandel, and Cabernet Sauvignon varietals.