Old vs. new urban: U.S. national mapping of the year of first development for urban areas, from 1940-2010

This product is a 100-m raster which classifies urban lands in the conterminous United States by the year in which they were first developed. The classification is based on housing density by era for 1940-2010 developed by the University of Wisconsin-Madison SILVIS lab. The classification was applied by identifying a housing unit density threshold which matched current-era development as represented by U.S. Census Urban Areas polygons, then re-applying that threshold to former eras back to 1940. The result is a national raster with eight classes, for the years 1940, 1950, 1960, 1970, 1980, 1990, 2000, and 2010, representing the year in which each pixel crossed the threshold of being developed. It is suitable for distinguishing areas which are primarily old urban as compared to new urban.