Urban blight is neither a problem of recent origin nor one which is confined tothe United States. With very few exceptions (notably Billy Penn's greene country town of Philadelphia), our cities developed uncontrolled and untrammeled by plan. Especially was this true during the nineteenth century, when cities burgeoned to accommodate and house the expanding economy wrought by the Industrial Revolution. The expansion carried within it the seeds of the twentieth century physical deterioration of our urban centers. As the industrial complex grew to meet the war demands of the 1940's and the frustrated consumer needs of the 1950's, blight began to threaten the very existence of our cities. However, it is not true, as some believe, that society stood idly by while this urban cancer developed. Society's initial attempts to eradicate urban blight were, indeed, as old as its very existence. The common law of public and private nuisances has been and continues to be antipathetic to deteriorating land usage. Of more recent origin, zoning control, building codes, and federal public housing projects aimed at this target. Nevertheless, these piecemeal attempts proved futile in and of themselves to provide an effective solution. The comprehensive power of government to renew, rehabilitate, and redevelop entire geographical areas within its jurisdiction-complementing effective programs of zoning regulation, building code enforcement, slum clearance, and. public housing-was exercised to restore our cities and to prevent further blight. This, then, is the sum of today's tools for effective urban renewal. Necessarily, comprehensive urban renewal has brought to the fore many new problems both within and without the compass of law. However, some problems are neither new nor peculiar to it alone. Rather, they are encountered at all levels of government and whether or not the concern is urban renewal. One of the latter, the cost attendant to the exercise of the power of eminent domain, is the general subject of this section. Here, the concern is not only how much government will be required to pay when it takes land or property by its sovereign right or pursuant to constitutional or legislative grant, but also the indirect costs that are levied upon government when it operates through traditional condemnation procedures. And it is of relatively minor significance whether the purpose of the taking be for a highway, slum clearance, public housing, industrial development, airport construction, or any other type of project. The question of cost is ever present.