Historical maps online
...) Finding this inspired me to do a bit of a search for other online historical maps of Britain which similarly attempt to cover the whole country. (There's a useful list of out-of-copyright maps here.) Old-maps.co.uk has been around a while and uses OS maps from the late 19th century. Vision of Britain (which site has lots of historical statistics which you can slice various ways, and which I must explore more thoroughly one day) is more sophistic...