Over a two-year period, photographer Jamey Stillings documented the transformation of an American landmark. The building of the structure that connects the Arizona and Nevada sides of a concrete arch appears in a coffee table book called The Bridge at Hoover Dam (

Nearly one million people visit the 76-year-old Hoover Dam each year. In 2010 the historic site greeted visitors with a new addition: a 1,900-foot bridge. The Mike O’Callaghan - Pat Tillman Memorial Bridge is a part of the Hoover Dam Bypass Project, which was built to alleviate traffic on Route 93. "Today, the bridge is significant for its aesthetic, functional and geographic connection to the Hoover Dam and for its technical achievement, crossing the Black Canyon over the Colorado River with the longest concrete arch span in the western hemisphere," Stillings writes in his book. To see some of his photographs from this project, check out the following slide show.

View a slide show of the bridge construction at Hoover Dam