Google added historic map overlays to its free interactive online globe of the world to provide views of how places have changed with time. Google Earth engineers digitized one of the largest US map collections and integrated the information into its program, which lets users virtually navigate the planet and swoop in for closer looks.

The collection of David Rumsey Historical Maps dated from 1680 to 1892 and included Cassini's Globe of 1790; Africa in 1787, and a map of Asia from 1710.

"It is wonderful to see the cutting edge technology of Google Earth introduce people to the geographic history of our world in a new and innovative way," Rumsey said.

"The cartographers who made these historical maps hundreds of years ago would be amazed and pleased to see their treasures in Google Earth."

Google also added an interactive National Geographic quiz focused on Africa.

There have been over 100 million downloads of the Google Earth program to computers since it was launched in June of 2005.