The term 'California Mountains, Informally' can be summarized as the Sierra Mountains. The Sierra Mountains are a mountain range in the western United States, located in the states of California and Nevada. They stretch 400 miles from north to south and 80 miles from east to west, forming a natural barrier between the Central Valley of California and the Great Basin. The highest peak in the range is Mount Whitney, which has an elevation of 14, 505 feet. The Sierra Nevada is home to numerous national parks, including Yosemite, Sequoia, and Kings Canyon.