In the late 1800s clipper ships and steam ships brought textiles and tea from Asia, along with whale oil, rice and other products.
Along the waterfront, shady characters made money shanghaiing sailors. Some seamen who disembarked on San Francisco's Barbary Coast after long ocean trips, were drugged and handed right back over to ship captains lacking a full crew. This, of course, meant more months or even years at sea.
The San Francisco Maritime National Historical Park is an outdoor museum on Hyde Street Pier. You can take tours of historic ships like the Balclutha and see visual representations of San Francisco's colorful, maritime past.
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More about the Barbary Coast Trail -- including links to an online trail map.