资料题：San Francisco today is a thriving city because of（　）。

Asked to name their favorite city, many Americans would select San Francisco.San Francisco began as a small Spanish outpost located on a magnificent bay.The town was little more than a village serving ranchers when the United States took possession of it in 1846 during the war with Mexico.San Francisco sprang into a city overnight because of the nearby discovery of gold in 1848.A great rush t California took place.Wagon trains plodded their dangerous way across 2000 miles of prairie(大草原) and mountains, while hundreds of sailing vessels made the equally hazardous(危险的)tip around the Horn.The vessels disgorged(放出)thousands of passengers, then the crews deserted their ships and hundreds of vessels were left to rot in the Bay.Within two years, California had enough population to become a state and San Francisco was for many years the hub of that newly-arrived population on.The city's present popularity is due to n excellent climate, an easy style of living, good food, and numerous tourist attractions..The city is famous for its cable cars which "clang and bang" up the steep hills, and for its excellent seafood stalls along the wharf.Most visitors arriving from nations in the Pacific Basin spend several days getting to know the town.