The Rock ‘n’ Roll Marathon Series is the largest running series in the world. Make Every Step Count is the charitable arm of the series and has to date raised hundreds of millions in 30 cities. The marathons are celebrations of community and giving, and in Las Vegas, the series is the only event for which the Strip shuts down. But the marathons had special significance this year with “Vegas Strong” on everyone’s mind after the recent shooting. Runners observed complete silence for 2 1/2 miles in memory of the fallen. Participants came from 73 countries. A third were first-time marathoners.