The subject of regional planning now stands high on the calendar of American social thinking. Miss Kimball, in compiling her admirable manual of information three years ago, was able to make a fair display of papers and documents on regional, rural, state, and national planning. Since that time the sheaf of materials has grown substantially in bulk and variety. This increase of interest in the topic was inevitable. As in the world of abstract ideas every attempt to cut through to the heart of a problem lands us in metaphysics, to use the penetrating observation of William James, so in the field of municipal development any effort to follow the filaments of city planning to their roots leads us beyond the immediate urban area into the large and indefinite region of which it is a part. Anyone who has for a moment got away from the political aspects of a specific city government and taken up some particular question, such as transportation, knows how quickly he is carried beyond the legal boundaries of his municipality into its regional, state, national, and even international, relations. If anyone, perchance, has doubts on the point, let him spend a few hours with the 1920 report of the New York-New Jersey Port and Harbor Development Commission. Of course to adepts this is all trite enough, but it is an indication of what must be the inexorable drift in the thinking of those who are concerned with anything more than the decorative aspects of municipal design.