 Northern California also contains redwood forests, along with the Sierra Nevada, including Yosemite Valley and part of Lake Tahoe, Mount Shasta (the second-highest peak in the Cascade Range after Mount Rainier in Washington), and most of the Central Valley, one of the world's most productive agricultural regions.The 48-county definition is not used for the Northern California Megaregion, one of the 11 megaregions of the United States.The megaregion's area is instead defined from Metropolitan Fresno north to Greater Sacramento, and from the Bay Area east across Nevada state line to encompass the entire Lake Tahoe-Reno area.