Yes, there's liquid gold hidden among the vines, part of an olive oil boom in recent years.
You can tour an orchard, learn what extra-virgin olive oil really means and taste your way through lemon-, herb- and even chocolate-infused olive oils. Harvest is usually around the end of the year, but any time is good for a visit.
Here are five recommended "pit" stops.
A family run winery whose owners branched out into olives some years ago, this estate produces four gourmet olive oils and has an onsite olive mill. If you're pressed for time you can do the "Splash and Dash" tasting, enjoying olive oils and the estate's red wine vinegars. Available April-November, Thursday-Sunday 2pm to 5pm and Friday-Sunday 2pm to 5pm, US$20 (NZ$23.6) per person.
For a more leisurely approach, take a tour and tasting, by appointment only and available at 10am, 12:30pm and 3:30pm daily.
You get a tour of the mill followed by sit-down tasting of olive oils, vinegars and syrups paired with estate wines, vegetables and other fresh edibles, US$45 (NZ$53) per person, 886 Rutherford Road, Rutherford, California.
Tailor your visit to be long or short, depending on your inclination. Stop by the winery tasting room in St. Helena (738 Main Street) to enjoy an olive oil tasting from 11am to 6pm, no appointment needed, US$5 (NZ$5.9) for a tasting of Prato Lungo and Napa Valley Select olive oils.
For a more in-depth look, visit the winery's Mayacamas Estate. You'll explore the grounds, see the vineyards and visit the oldest olive orchard in Napa County, planted in the 1870s. Reservations required, US$85 (NZ$100) a person.
During harvest, you can watch the mill in progress from a viewing platform and all visits end with a tasting of limited production wines and a sample of LMR organic Napa Valley Select Extra Virgin Olive Oil.
McEvoy Ranch started when Nan McEvoy, part of the family that founded the San Francisco Chronicle, was looking for a place in the country. She settled on 23 hectares in Marin County. Inspired by her love of Tuscan olive oil, she worked with Italian expert Maurizio Castelli to create what is now a thriving business. The ranch is open only at certain times of the year, so you'll need to plan your visit.
This year, tours will be offered April 12, June 14, July 26 and October 4. There'll be a birding tour April 26, a cooking demonstration August 2, and a wreath-making workshop November 1. Orchard walking tours start at US$30 (NZ$35.4) per person; touring the gardens and having lunch is US$90 (NZ$106).
For reservations book online at mcevoyranch.com. McEvoy Ranch also recently opened a third retail location at San Francisco International Airport's Terminal 3.
The Olive Press offers a tour of its mill in Sonoma where you can learn about how the oil is made, get tips on how to taste oil like a professional and browse the large store.
Tour reservations are required at least a week in advance, and cost varies from free to US$20 (NZ$23.6) per person depending on activities selected. The mill is located within Jacuzzi Family Vineyards so there's a complimentary wine tasting as well.
Mill: 24724 Highway 121 (Arnold Drive), Sonoma, California. Napa tasting room: 610 First Street, Napa. Hours: Monday, Wednesday-Saturday 9am-7pm, Tuesday 9am-8pm, Sunday 9am-6pm.
Walk into the downtown Napa tasting room of Lucero Olive Oil and you know you're in for some serious tasting. The walls are lined with bottles of olive oil including several infused oils that range from zippy Meyer lemon to a chocolate-infused oil that is delicious on ice cream.
Lucero also produces a range of balsamic vinegars, table olives, tapenades and mustards which are available for tasting. The company mill and groves are based in Corning, a major olive producing area in northern California and there's also a tasting room in Portland, Oregon.
Napa tasting room: 1012 First Street, Napa. Open Sunday-Monday 10am-10pm, Friday-Saturday 10am-11pm.