You can find it in the "layers" menu. Click on "Featured Content" and there you can find the "Rumsey Historical Maps".
There are a bunch of maps available, lets take a look:
- The World Globe in 1790
- North American in 1733
- The United States in 1833
- Lewis and Clark maps from 1814
- New York in 1836
- San Francisco in 1853
- South America in 1787
- Buenos Aires in 1892
- Asia in 1710
- Tokyo in 1680
- The Middle East in 1861
- England, Wales in 1790
- London in 1843
- Paris in 1716
- Africa in 1787
- Australia Southeast in 1844