Los Angeles, the seat of Los Angeles County, is the largest city in California and the second-most populous in the United States, with roughly 3.9 million residents. It occupies a coastal basin in Southern California framed by the Pacific Ocean to the west and the Santa Monica and San Gabriel mountains to the north and east. Los Angeles County, the most populous county in the country with about 9.7 million residents, contains 88 incorporated cities, but the city of Los Angeles itself remains the region's gravitational center. The city grew from a Spanish and Mexican pueblo into an American metropolis on the strength of successive booms—railroads, oil, citrus and agriculture, the port, aviation, and above all the motion-picture industry, which made Hollywood a global brand. Its economy today is unusually diversified: entertainment, international trade through the Port of Los Angeles and the neighboring Port of Long Beach, aerospace, technology, fashion, manufacturing, and tourism. The Port of Los Angeles is the busiest container port in the Western Hemisphere. Los Angeles is famously decentralized, a collection of hundreds of distinct neighborhoods rather than a single dense core, strung together by freeways and an expanding rail network. Downtown Los Angeles has re-emerged as a residential and cultural center with historic theaters, museums, and new housing, even as Hollywood, the Westside, and the coastal neighborhoods each carry their own gravitational pull. The University of California, Los Angeles and the University of Southern California anchor a large higher-education and research sector. The city's residents include creative and entertainment professionals, workers in aerospace and logistics, students at major universities, and communities drawn from across the globe, giving Los Angeles one of the most diverse populations of any major American metropolis. A mild Mediterranean climate, proximity to beaches and mountains, and a deep cultural calendar keep the city's appeal broad, from hillside bungalow districts to coastal communities and the residential expanse of the San Fernando Valley.