The evolving Interstate Highway System and the changing geography of the United States

Abstract

The Interstate Highway System is a product of the 1930s and 1940s, yet remains essential to U.S. transportation in 2012 and for the foreseeable future. This analysis examines how the Interstate Highway System has changed since its inception in 1938, first map in 1947, and the beginning of construction in 1956. The mileage has grown considerably, allowing for many new routes, and the spatial coverage of the network has been extended to allow many new metropolitan areas to be connected. This has lowered connectivity but increased the metropolitan population served. A GIS dataset was created for the 1947 network, allowing it to be compared to the current network using standard accessibility measurement techniques. This research shows that the Interstate System has not kept up with population shifts in the South and West, and there is no correlation between accessibility change and population change. The greatest improvements have in fact taken place in the densest part of the network, not where population or traffic growth has been greatest. It has therefore reinforced advantages held by places already well placed on the original 1947 network. The old American Manufacturing Belt continues to provide an effective regionalization for capturing variations in the Interstate network, though it has become the Rustbelt and is of declining importance within the country.