Signed by President Eisenhower in 1956, the act authorised a 41,000-mile Interstate Highway System and committed about 25 billion dollars in federal funds, reimbursing states for 90 per cent of construction costs. Justified partly on Cold War defence grounds, it became the largest public works programme in American history. Routed through cities at low land-acquisition cost, the new urban expressways cut through and demolished many working-class and minority neighbourhoods. The system entrenched automobile dependence and accelerated suburban sprawl and central-city decline.
The interstate programme remade the spatial form of metropolitan America around the car and dealt lasting damage to many urban neighbourhoods.
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