September 11: Bells toll as the US marks 22 years since 9/11, from ground zero to Alaska

Americans are looking back on the horror and legacy of 9/11, gathering Monday at memorials, firehouses, city halls and elsewhere to observe the 22nd anniversary of the deadliest terror attack on U.S. soil.

Commemorations stretch from the attack sites -- at New York's World Trade Center, the Pentagon and Shanksville, Pennsylvania -- to Alaska and beyond.