Perhaps the toughest challenges associated with building the long-awaited bridge linking Arizona and Nevada had less to do with technology and the daunting dimensions and more to do with respecting the true engineering marvel 1,500 feet upstream. At least that is the opinion of one well-respected civil engineer.

"I think the challenge was to make it come up to the iconic standards of the Hoover Dam, building something in such close proximity to a world-class structure like that," said Henry Petroski, a civil engineering professor at Duke University. "The engineers involved were very conscious of this, that they were working with a site that had to be respected."