Mike O'Callaghan-Pat Tillman Memorial Bridge is along US 93, about 5.5 mi. n.e. of Boulder City. Linking Nevada and Arizona, this arched, 1,900-foot-long concrete-and-steel span is some 1,500 feet downstream from Hoover Dam. Opened in 2010, the bridge was built to replace a longstanding traffic bottleneck: the two-lane section of US 93 that crossed the Colorado River atop Hoover Dam (now SR 172).
Thanks to a 6-foot-wide pedestrian sidewalk running its length, the bridge—which honors former Nevada Governor Mike O'Callaghan and Afghanistan war hero Pat Tillman—has become a major attraction. Lined with etched information panels, the sidewalk is accessible only from the Nevada side (it dead-ends at the Arizona side); follow signs to the Hoover Dam Access Road (SR 172) exit. The parking lot for visitors is about 2 miles down the road; if the bridge lot is full, an overflow lot is a couple hundred yards further down.
From this lofty perch you'll have a grand view of the Hoover Dam, not to mention a jaw-dropping (and stomach-churning, for those afraid of heights) perspective of the turquoise Colorado River 900 feet below, wedged between the rock cliffs that form Black Canyon. Prime time for photography is mid- to late-afternoon.
Note: Before reaching the bridge and Hoover Dam area you'll pass through a vehicle inspection security station. A switchback trail with 70 steps (and paved, wheelchair-accessible ramps) provides access to the pedestrian sidewalk.