A fairly simple question: from what single point could you see the most US states? It seems like it should be a popular tourist attraction.
Mt Greylock, the highest point of Massachusetts provides a view of at least 5 states.
- New Hampshire
- New York
Hiking to the top gives one a sense of real accomplishment and the 360 degree vistas are your well earned rewards. North into Vermont/New Hampshire, south into lower Mass./northern Connecticut, east towards Boston, west into the Adirondacks of New York State.
Information comes from berkshirehiking.com
The four corners area would be one spot where you would be guaranteed to see four states (New Mexico, Arizona, Utah, Colorado). It already is a tourist attraction.
Perhaps there may be a spot in the Appalachian Mountains in southern part of New Hampshire or Vermont, where on a really clear day you might be able to see five states. But this is just a guess based on topography.
While Four Corners would be the only one where 4 states visibility is guaranteed, on a clear day you can see 4 states from the Skydeck of Willis (Sears) Tower in Chicago:
On a clear day, you can see four states – Illinois, Indiana, Wisconsin and Michigan. Visibility from the Skydeck is approximately 40-50 miles (65 – 80 kilometers).
The Four Corners Monument...
The Navajo Nation cordially welcomes you to one of our most unique landmarks - The Four Corners. This is the only place in the United States where four states intersect at one point: Arizona, New Mexico, Utah and Colorado. This location is very remote as you will experience when visiting.
The original marker erected in 1912 was a simple cement pad, but has since been redone in granite and brass. The Visitor Center is open year round, and features a Demonstration Center with Navajo artisans. Navajo vendors sell handmade jewelry, crafts and traditional Navajo foods nearby.
Also see the Wiki article: http://en.wikipedia.org/wiki/Four_Corners_Monument
If you consider a man-made tower there was Wonder Tower in Genoa, Colorado (now closed) in Eastern Colorado that you could see 6 States - Colorado, Kansas, Nebraska, Wyoming, New Mexico and South Dakota:
From the International Space Station you can see all 50 states at once. It is a tourist destination but ticket prices are... astronomical.
Related question on Space.SE:
How could I travel to space as an ordinary citizen?
There is a point in Western Oklahoma, near Boise City that is within 30 miles of five different states. If you were about 500 feet above the ground there, you'd be able to see Kansas, New Mexico, Oklahoma, Texas, and Colorado.
A quick glance at Google Street View shows no skyscrapers, but small hills, probably less than 500 feet tall.