Imagine flying high above the Rocky Mountains in late 1939, looking downwards towards the peaks below. Now picture yourself staring down at the city of Denver around the same time, peering onto the tops of residential buildings, factories, and feedlots. Until time travel is feasible, this probably isn’t possible for most of us. Of course, for those with a penchant for the past, aerial photographs of Colorado for the period from 1938 to 1947 are available at this website, created and maintained by the University of Colorado Libraries Map Library. Originally created by the U.S. Forest Service, these maps cover eight counties in the state, including Boulder, Clear Creek, Eagle, and Larimer. Visitors can search or browse these photographs by using a geographic keyword search, and also read the metadata associated with each item.