The Grand Canyon is found in Arizona in the United States. A canyon is a deep narrow valley with steep sides.
You can learn more by reading 1908: Grand Canyon Becomes a National Monument. National Geographic have many good resources besides the magazine such as Grand Canyon Facts from the National Geographic Visitor Center, and an interactive map. There is also the 45 minute documentary The grand canyon (National geographic) HD.
A virtual tour of The Grand Canyon from the National Park Service, uses Google Earth and you need the Google Earth plug-in to view that. If you are interested in archeology you can have a look at another virtual tour which starts at the south rim.