Oakland/oklnd/ is a major West Coast port city in the U.S. state of California. The Port of Oakland is the busiest port for San Francisco Bay and all of Northern California. Oakland is the third largest city in the San Francisco Bay Area, the eighth-largest city in the state, and the 47th-largest city in the U.S. with a population at the 2010 U.S. Census of 390,724. Incorporated in 1852, Oakland is the county seat of Alameda County. It serves as a major transportation hub and trade center for the entire region and is also the principal city of the Bay Area Region known as the East Bay. The city is situated directly across the bay, six miles (9.7km) east of San Francisco. Oakland's territory covers what was once a mosaic of coastal terrace prairie, oak woodland, and north coastal scrub. Its land served as a rich resource when its hillside oak and redwood timber were logged to build San Francisco, and Oakland's fertile flatland soils helped it become a prolific agricultural region. In the late 1860s, Oakland was selected as the western terminal of the Transcontinental Railroad. It continued to grow in the 20th century with its busy port, shipyards, and a thriving automobile industry. Following the 1906 San Francisco earthquake, many San Franciscans relocated to Oakland, enlarging the city's population, increasing its housing stock and improving its infrastructure. A steady influx of immigrants during the 20th century, along with thousands of African-American war-industry workers who relocated from the Deep South during the 1940s, have made Oakland one of the most ethnically diverse major cities in the country. Oakland is known for its history of political activism, as well as its professional sports franchises and major corporations, which include health care, dot-com companies and manufacturers of household products. The city is a transportation hub for the greater Bay Area, and its shipping port is the fifth busiest in the United States. Oakland has a Mediterranean climate with an average of 260 sunny days per year. Lake Merritt, a large estuary centrally located east of Downtown, was designated the United States' first official wildlife refuge. Jack London Square, named for the author and former resident, is a tourist destination on the Oakland waterfront.