While the US contends with the destruction caused by two ferocious hurricanes in three weeks, Americans also are marking the anniversary of one of the nation's most scarring days.
Thousands of September 11 victims' relatives, survivors, rescuers and others are expected to gather at the World Trade Center to remember the deadliest terror attack on American soil.
Sixteen years later, the quiet rhythms of commemoration have become customs: a recitation of all the names of the dead, moments of silence and tolling bells, and two powerful light beams that shine through the night.
Nearly 3,000 people died when hijacked planes slammed into the trade center, the Pentagon and a field near Shanksville, Pennsylvania, on September 11, 2001, hurling America into a new consciousness of the threat of global terrorism.
President Donald Trump, a native New Yorker observing the anniversary for the first time as the nation's leader, is scheduled to observe a moment of silence at about the time the first airplane hit, joined by first lady Melania Trump.