Greater Sacramento straddles two key regions of California, the Central Valley and the Sierra Nevada mountains and is overlapped by the cultural influences of three areas, the Bay Area, Eastern California and Northern California. An increasing phenomenon taking shape in Greater Sacramento is growth of urban sprawl as Sacramento and its metropolitan area continue to expand. The growth is due in part to first, higher costs of living in the Bay Area which have caused commuters to move as far as Yolo and Sacramento counties and more recently, growth and rising living costs in the core of Sacramento, building up more areas in the surrounding counties for commuters.