The Valley is home to Nevada's three most populous incorporated cities: Las Vegas, Henderson, and North Las Vegas. The terms Las Vegas and Vegas are used interchangeably to refer to the Valley, the Strip, and the city, as well as by the Las Vegas Convention and Visitors Authority to denote the region. Geographically, the Valley is defined as that part of Nevada located between Lake Mead and the Sierra Nevada mountain range. But due to its location at the crossroads of the American West, the term "Valley" also applies broadly to reference areas with similar characteristics including climate, culture, and geography. The Valley has been described as a desert oasis, with sunny days and cold nights. It is located in a valley formed by the Clark and Mojave Deserts, with mountains rising up around it. This natural harbor was first settled by Native Americans, who named it "Kanab". When European settlers arrived in the 19th century, they changed the name to "Las Vegas" after the famous casino town in Italy. Although tourism is the main industry of the Valley, agriculture also plays an important role because it provides two-thirds of the region's employment. The Valley is known for its grapes, vegetables, flowers, and livestock. It is also the largest producer of apples in the United States. The population of the Valley is estimated to be approximately 1 million people.