The duration of the eclipse will be about two and a half minutes at maximum, at the center line. The width of visibility will be about 115 km.
This will be the first total eclipse to pass over any part of the United States since 1991, when a total eclipse passed over Hawaii. Plan your trip now! (Ten years into the future is not as far out as you think...)
USA Total Solar Eclipse 2017, everything you need to know to plan to see the eclipse, including links to details maps, courtesy of Dan McGlaun
Hermit Eclipse: Total Solar Eclipse: August 21 2017 (with some excellent maps)
Path of Total Solar Eclipse of 2017 Aug 21 (a NASA website with coordinates, which links to a map of the globe with the eclipse's path)
Wikipedia: Solar eclipse of August 21, 2017