The following zoning districts are hereby established:

Unless otherwise indicated, the boundaries between districts are either the center lines of streets, lanes, lakes, watercourses and rights-of-way, or such lines extended or lines parallel thereto. Where the boundaries of a single district are indicated as a watercourse, right-of-way or power line, for any portion of its length, the district so indicated shall be construed to apply to the entire bed of the street, lane, lake, watercourse or right of way lying within such portion of its length. Where uncertainty exists as to the location of such boundaries as shown on the Zoning Map, the following rules shall apply:

Whenever federal or state-owned property is included in one or more zoning districts, it shall be subject to this Zoning Code only insofar as permitted by the Constitution and laws of the United States and of the Commonwealth.