[cannonedhamster]

The sidewalk. And the street right of way extends beyond just the physical street in most places.

[jessriedel]

This comment is pedantic. Yes, there are special regulations about homeowners in some areas having to place and maintain sidewalks along their property. (In other areas, they are owned and/or maintained by the city.) That's very distinct from setbacks, which prohibit construction for a depth much further than the width of the sidewalk.

[asdff]

Your lot usually doesn't include the sidewalk or the treelawn for that matter, although you are usually held responsible for its maintenance.