The cable cars of San Francisco are not only an icon, they are also part of the world's last manually operated cable car system. Between 1873 and 1890, 23 lines crisscrossed the city. Today only three remain, and the cars are one of two National Historic Streetcar Landmarks in operation (New Orleans’ St. Charles streetcar line is the other). Riding them is a must, of course, but to understand the history of the system, how they work, and what is causing that rumbling beneath your feet, check out the Cable Car Museum in the Nob Hill neighborhood. You'll trace San Francisco's cable car from their creation by a man named Andrew Smith Hallidie in 1873, who based the design on early mining conveyance systems, through the great earthquake of 1906, two World Wars, and the attempts to remove cable cars from San Francisco, to their worldwide status as a symbol of San Francisco. The museum houses a collection of historic cable cars, photographs, and mechanical displays. But this is more than just a museum, it is also the actual hub of San Francisco's cable car system where you can watch the cables turn and churn, imagining the cars outside being pulled up and down hills. And--- it's free!