619,000 buildings, 544,033 of them list the year they were built in Portland. Justin Palmer of GitHub created this beautiful map of Portland, Oregon's buildings by age with TileMill. The color scheme that he chose, as well as the varying patterns of neighborhoods, some in neat post-war rows, some in more organic arrangements, makes for a really pleasing visual. Read more about Justin's work in his post Portland, Oregon: The Age of a City