One of the reference questions our library occasionally receives is how to find out the number of registered motor vehicles in Colorado. This information is contained in the Department of Revenue Annual Report (which, by the way, contains many other statistics such as taxes, liquor licenses, the Colorado Lottery, and more.) Our library has digitized the reports going back to 1942, which can be used for understanding changes over time. For instance, fifty years ago, Colorado had approximately 1.7 million registered vehicles. As of 2015, the number was over 5.5 million!