Mappery.com has at least one map for every country on the planet, each of the 50 U.S. states and all the Canadian provinces. It also has a host of maps from previous eras. Here’s a slice from a 1948 Yosemite National Park map:
View the whole thing here. If you scroll down, you find more maps from nearby, if available.
You can even create your own online map room, if you’re into that sorta thing.
The technology is pretty slick: if you click on a full size version of a map, it’ll let you zoom into individual parts and slide from one locale to another as you’d do with Google maps.