Measure A, the Building Height Freeze was passed by Voter Initiative in 1985. It requires a a vote of the electorate before the City Council can approve projects that exceed the height limits in place at that time.
Height limits are also specified in the City’s General Plan. Sometimes they match the Measure A limit, sometimes they are lower. Measure A was a quickly thrown-together and imperfectly written citizen’s backlash in response to the City raising height limits to approve 10-story office buildings north of the BART station. The General Plan, on the other hand, was developed over several years with a lot of thought and citizen input going into it. The General Plan is the City’s vision of what it should become. Measure A was more of a reflexive swipe by the voters against a 1985 City Council that went too far ... but it matters, because nothing much has changed since then.