Hmm, I'm not sure what you mean by "first two squares of sidewalk". I lived on Coso Ave in Bernal Heights, where a bunch of garage doors are right next to the sidewalks. Some of my neighbors would park their cars in their driveways, with the tail end sticking out into the street, and blocking sidewalk users from crossing their driveways as a result. I can't imagine how that could be legal.
Typically sidewalks are not uninterrupted planes of concrete, but are divided into squares so that in case there is sidewalk buckling, they have some give and don't break up the whole thing, plus repair is made easier.
So, usually the first two squares' width belong to the municipality, any others are property of the residence.
