A "blighted district" is a district, originally developed for residence or industry, in the future of which people have lost confidence.
The causes of such "blight" are manifold. The most familiar case is that of a residential district into which there have begun to creep various uses threatening rapid destruction of its value for residences - such new uses as sporadic stores, or factories, or junk yards. It is not that a few such inappropriate uses really spoil the district, but that people having lost confidence, start a panic like a "run on the bank." Hundreds of them hurry up to "unload" their properties at a sacrifice for any kind of use, no matter how objectionable to their neighbors - and the "bright" is on! Dwellings worth in the aggregate millions of dollars for the purposes for which they were built, and physically fit to serve those purposes for many years to come, with a moderate investment in alterations and improvements, are thus annually abandoned to purposes for which they are not fit, or are left to stand practically idle. Expensive public services of water, gas, electricity, sewers, and transportation are maintained at great waste in order to get through the "blighted" district to the more distant and newly fashionable location.
The total economic loss is enormous, and this loss and the risk of it are paid by the people, in the price of house rents or otherwise, as inevitably as they pay the price of the enormous fire losses, either directly or through insurance.
Again, miles of streets and sewers and other utilities, such as are ordinarily built when land is newly subdivided for dwellings, need never be constructed if we know that these areas will be devoted mainly to large factories. Industry will be more efficient, as well as homes more wholesome, if kept generally separate. Separation need not mean great distances for workers to travel. Concentration of uses and a fair apportioning of districts should reduce the amount of all transportation and secure economies not only directly for the worker but indirectly in the costs of production and marketing of goods.
If zoning can reduce the cost of living, why not have it?
When a zoning law is properly drawn there is no doubt that the courts will support it. Enough favorable decisions have been handed down to show that the courts regard regulation of the uses of land and structures thereon, in accordance with the kind of district in which they are situated, as a reasonable exercise of the police power "for the public health, safety, and general welfare."