Space becomes public, and can really only remain public, through the practice of collective power. The government can exercise its power on behalf of the people to acquire property, forcing unwilling private owners to surrender their land if necessary. Private property can also become public through adverse possession as a result of continual use. To avoid becoming dedicated to public use, some properties like Rockefeller Center that welcome the public famously close periodically to assert their private rights.
Yet the process can work in reverse as well. In the absence of collective power, property can stop being public, even if it is still ostensibly publicly owned. This happens frequently enough in cases of abandonment, when fences or signage prohibit the public from using a space the government no longer wants to pay to maintain. Uglier cases entail the appropriation of public space by private interests without resistance from the appropriate authorities.
That is precisely what happened at 3059 Bainbridge for far too many years. The adjacent homeowners blatantly enclosed a section of the public sidewalk to create more private parking for themselves. This was reported to the City at least as early as 2008, but it was not removed until a couple weeks ago. For more than six years, parents with strollers and others were inconvenienced as they squeezed through an ugly and uncomfortably narrow space between a utility box and a cyclone fence.

