The city forms the most populated part of a regional area called the Conejo Valley, which includes Thousand Oaks proper, Newbury Park, Westlake Village, Agoura Hills, and Oak Park. The Los Angeles County/Ventura County line crosses at the western city limits of Westlake Village. The population was estimated to be 128,374 in 2012, up from 117,005 at the 2000 census.
Thousand Oaks and Newbury Park were part of a master planned city, created by the Janss Investment Company in the mid-1950s. It included about 1,000 custom home lots, 2,000 single-family residences, a regional shopping center, industrial park and several neighborhood shopping centers. The median home price is around $673,000. It is located in the northwestern part of the Greater Los Angeles Area. In 2006, the city was named one of Money magazine's Best Places to Live.
The area was once occupied by the Chumash people, and 2000-year-old cave drawings may still be seen at the Chumash Indian Museum, 3290 Lang Ranch Parkway, in the Lang Ranch section of the city. The Chumash village was known as Sap'wi, which means "House of the Deer."
The area's recorded history dates to 1542 when Spanish explorer Juan Rodriguez Cabrillo landed at Point Mugu and claimed the land for Spain. It eventually became part of the Rancho El Conejo land grant by the Spanish government, thus becoming the basis of the name Conejo Valley (conejo means "rabbit" in Spanish, and there are many in the area). It served as grazing land for vaqueros for the next fifty years.
The Janss family, developers of Southern California subdivisions, purchased in the early 20th century. They eventually created plans for a "total community" and the name remains prominently featured in the city.
Jungleland USA was one of Southern California's first theme parks. Wild animal shows entertained thousands in the 1940s and 1950s. Many TV and movie productions used the park's trained animals and were filmed there, including Birth of a Nation, Tarzan, and The Adventures of Robin Hood. Jungleland closed down in May 1968, in part due to competition from other amusement parks such as Knott's Berry Farm and Disneyland. The Thousand Oaks Civic Arts Center today stands on the site of the park.
The City of Thousand Oaks was incorporated on October 7, 1964, the first incorporated city in the Conejo Valley. It is known for being entirely a planned community, as the city is one of few that have actually stayed with the master plan. As a result, the city has fewer of the problems of other cities of similar size, such as traffic congestion and pollution, although increased development in Moorpark and Simi Valley in the late 1990s and early 2000s caused the Moorpark Freeway (Highway 23) to become heavily congested during both morning and afternoon rush hours. A major widening project began in 2008 to alleviate most of this congestion. Because of its desirable environment and location, property values have appreciated more than 250% in less than ten years, primarily during the mid-90s to early 2000s.
Newbury Park is located in the westernmost part of the city within the 91320 zip code. This area was once controlled by Ventura County as an unincorporated area, but was later annexed by the city of Thousand Oaks through votes by Newbury Park communities. The only communities that chose to remain county areas are Casa Conejo, which was Newbury Park's first planned community built from 1960 to about 1965, and Lynn Ranch, an old neighborhood in the western portion of the city.
Thousand Oaks also annexed the parts of neighboring Westlake Village (then simply known as "Westlake") that were located in Ventura County, in two portions in 1968 and 1972.