One of the most valuable websites for discovering old maps around the world, OldMapsOnline.org has just gotten a lot more useful. The original interface for the website was innovative and allowed you to select a part of the world in a rectangle and then see a list of the maps available. The updated interface focuses more on a particular location and makes finding a pertinent map much easier. The origin of the website is explained as follows.
OldMapsOnline developed out of a love of history and heritage of old maps. The project began as a collaboration between Klokan Technologies GmbH, Switzerland and The Great Britain Historical GIS Project based at the University of Portsmouth, UK thanks to funding from JISC. Since January 2013 is the project improved and maintained by volunteers and the team of Klokan Technologies GmbH in their free time.
OldMapsOnline.org indexes over 400.000 maps. This is only thanks to the archives and libraries that were open to the idea and provided their online content. All new participants are warmly welcomed.The website is essentially an interactive portal to many huge online map suppliers including the U.S. Geologic Survey, The David Rumsey Map Collections, the New York Public Library, the British Library, The Harvard Library and many more.
You begin a map search by entering a place name. I decided to start with Provo, Utah. The maps found were associated with the "Parent Place" Utah. Here is an example of an old map of Utah from 1879.David Rumsey Map Collection. These are all very high quality maps, although some of them are only available for a fee. Here is the part of the map above showing Provo, Utah:
This website has always been on my list of one of the most valuable places to see old maps. You might want to do a little exploration yourself. Here is a more recent USGS map of the Provo, Utah area: