Though California might be seen as a progressive state, San Francisco was relatively late to the party in setting up a public bike sharing system (maybe not for the US, but compared with other global cities).
Launched in 2013, there are 700 or so stations in San Francisco and Silicon Valley and 4,500 bikes for hire.
It is available only for adults (not cool for teenagers), who have pre-registered, and is intended for short point to point rides, rather than all day hire.
The bikes look like the standard, solid, heavy urban rental bike, similar to the Parisian Velib’. Step-through frame, adjustable saddle, chain and spoke guards, grip shifters (my nemesis) and hub gears, flat pedals with reflectors, slick tyres and mudgards (fenders). The stations repurpose 2-4 cars each, replacing them with parking for I guess 15-30 bicycles.
Not having used it, I can’t say how well it works, but didn’t notice anyone riding one while I was in town. Nonetheless I think this is a good initiative, even if it takes a while to build traction (by generally improving the cycling environment and cyclist safety).