Data from: A century of sprawl in the United States

The urban street network is one of the most permanent features of cities.
Once laid down, the pattern of streets determines urban form and the level
of sprawl for decades to come. We present a high-resolution time series of
urban sprawl, as measured through street network connectivity, in the
United States from 1920 to 2012. Sprawl started well before private car
ownership was dominant and grew steadily until the mid-1990s. Over the
last two decades, however, new streets have become significantly more
connected and grid-like; the peak in street-network sprawl in the United
States occurred in ∼1994. By one measure of connectivity, the mean nodal
degree of intersections, sprawl fell by ∼9% between 1994 and 2012. We
analyze spatial variation in these changes and demonstrate the persistence
of sprawl. Places that were built with a low-connectivity street network
tend to stay that way, even as the network expands. We also find
suggestive evidence that local government policies impact sprawl, as the
largest increases in connectivity have occurred in places with policies to
promote gridded streets and similar New Urbanist design principles. We
provide for public use a county-level version of our street-network sprawl
dataset comprising a time series of nearly 100 y.