Napa County is a county located north of San Pablo Bay in the U.S. state of California. It is officially one of the nine San Francisco Bay Area counties, and one of four North Bay counties. The county is coterminous with the Napa, California, Metropolitan Statistical Area. As of the 2010 census the population is 136,484. The county seat is Napa. Napa County was one of the original counties of California, created in 1850 at the time of statehood. Parts of the county's territory were given to Lake County in 1861. The word napa is of Native American origin and has been variously translated as "grizzly bear", "house", "motherland", and "fish". Of the many explanations of the name's origin, the most plausible seems to be that it is derived from the Patwin word napo meaning house, although local residents will often cite an urban legend that gives the translation as "you will always return".
 
Napa County, once the producer of many different crops, is known today for its wine industry, rising in the 1960s to the first rank of wine regions with France, Italy, Portugal and Spain.

In prehistoric times, the valley was inhabited by the Patwin Native Americans, with possible habitation by Wappo tribes in the northwestern foothills. Most villages are thought to have been constructed near the floodplains of watercourses that drain the valley. Their food consisted of wild roots, acorns, small animals, earthworms, grasshoppers, and bread made from crushed California buckeye kernels. In winter they would construct huts made of tree branches. In summer they camped near rivers and streams. In winter months, they were half clad in wild animal skins and at other times they wore no clothing. The maximum prehistoric population is thought not to have exceeded 5000 persons.
 
In 1776, a fort was erected by the Spanish Governor, Felipe de Neve a short distance northwest of Napa, on an elevated plateau. Russians from Sonoma County's Fort Ross grazed cattle and sheep in the Napa Valley in the early 19th century and in 1841 a survey party from the fort placed a plaque on the summit of Mount Saint Helena.
 
Francis Castro and Father Jose Altimura were the first Europeans to explore the Napa Valley in 1823.  When the first white settlers arrived in the early 1830s, there were six tribes in the valley speaking different dialects and they were often at war with each other. The Mayacomos tribe lived in the area where Calistoga was founded. The Callajomans were in the area near where the town of St. Helena now stands. Further south, the Kymus dwelt in the middle part of the valley. The Napa and Ulcus tribes occupied part of the area where the City of Napa now exists while the Soscol tribe occupied the portion that now makes up the southern end of the valley. Many of the native peoples died during a smallpox epidemic in 1838. Settlers also killed several over claims of cattle theft.
 
During the era between 1836 and 1846, when California was a province of independent Mexico, the following 13 ranchos were granted in Napa County.

George Calvert Yount was an early settler in Napa County and is believed to be the first Anglo-Saxon resident in the county. In 1836 Yount obtained the Mexican grant Rancho Caymus where he built what is said to be the first log house in California. Soon afterward, he built a sawmill and grain mill, and was the first person to plant a vineyard in the county. Following Yount's death in 1865 at age 71, the town of Yountville was named in his honor.
 
Following his marriage to General Vallejo’s niece Maria Guadalupe Soberanes, Edward Turner Bale became a citizen of Mexico and was granted Rancho Carne Humana in the northern end of the valley. Bale completed building the Bale Grist Mill a few miles north of St. Helena in 1846. Colonel Joseph B. Chiles a guide for one of the earliest immigrant trains to California, was granted Rancho Catacula in 1844.
 
The Town of Napa was founded on Rancho Entre Napa by Nathan Coombs in 1847.
 
Following the event of the Mexican–American War, Bear Flag Revolt in 1846 and the Mexican Cession in 1848, settlers were granted deeds from the original ranchos during the 1850s through 1870s. To this day, a number of streets and landmarks around the valley reflect the names of these ranchos and original grantees.
 
John Patchett opened the first commercial winery in the county in 1859. The vineyard and wine cellar were located in an area that is now in the city limits of Napa. After working as a winemaker for Patchett, Charles Krug founded his own winery in St. Helena 1861.

Napa Valley is widely considered one of the top American Viticultural Areas in California, and all of the United States, with a history dating back to the early nineteenth century. By the end of the nineteenth century there were more than one hundred and forty wineries in the area. Of those original wineries several still exist in the valley today including Charles Krug Winery, Shramsburg, Chateau Montelena, Nichelini and Beringer. Viticulture in Napa suffered a setback when prohibition was enacted across the country in 1920. Furthering the damage was an infestation of the phylloxera root louse which killed many of the vines through the valley. These two events caused many wineries to shut down and stalled the growth of the wine industry in Napa County for years. But for many Italian and Swiss families as farm labor in the vineyards, Prohibition offered the unique opportunity for the growing and shipping of grapes to immigrant homewinemakers across the country. Charles Forni, who received a gold coin as his first U.S. dollar upon arriving, rose to be a large shipper. The Mondavi family came West from the Minnesota ore-country to Lodi to ship grapes to the "Italian Club" miners. When Prohibition stopped in 1933, the price of grapes crashed to below $24 per ton. Then A.P. Giannini, founder of Bank of America at San Francisco, started to promote to rebuild the commerce of wine and viticulture. Following the Second World War, the wine industry in Napa again began to grow. But cattle and prunes were king.
 
In 1965, Napa Valley icon Robert Mondavi broke away from his family's Charles Krug estate to found his own. This was the first new large scale winery to be established in the valley since before prohibition. Following the establishment of the Mondavi estate, the number of wineries in the valley continued to grow, as did the region's reputation. Consumer trends followed the 60s free lifestyle for experimentation. The old "paesano" customers of "dego red" gallon jug wines changed to young women who considered white wine, not beer, as their new drink of choice for romance. Robert Mondavi Winery attracted new wine aficionados by introducing the larger, 1.5 wine bottle for an image of affordable quality.