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US interstates: facts about 50 years of road construction

America's Interstate Highway System has been called an economic and democratizing force that's the envy of many other countries. The system, which is celebrating its 50th anniversary, bears the name of President Dwight D. Eisenhower, who signed the Federal Highway Act of 1956 that got the ball – and the earthmovers – rolling. In 1994, the American Society of Civil Engineers classified it as one of the Seven Wonders of the United States, along with such landmarks as the Golden Gate Bridge and Hoover Dam.

Facts about the interstate system:

Started: 1956

First segments: In Missouri and Kansas

Length: 46,876 miles

Cost: approx. $129 billion

Ownership: States own and operate

Completion: Still unfinished; connector north of Philadelphia currently under construction

Myth: One in five miles is straight so airplanes can use for emergency landings

Five border-to-border routes: I-5, I-15, I-35, I-55, I-65, I-75, I-95

Route passing through the most states: 1-95 (seven states)

– Federal Highway Administration