Coloradoans and people across the nation are marking 18 years since the 9/11 attacks. Hundreds gathered at Red Rocks this morning for the annual "Stairclimb" to remember the people who were killed in New York, Washington, and Pennsylvania. The climb is centered on firefighters, but plenty of families and friends showed up to circle the amphitheater nine times; that climb would equal 110 stories, matching the World Trade Center's twin towers that were leveled in the attack.