Bells tolled at 8:46 a.m. ET this morning, the exact moment when the first hijacked airplane struck the World Trade Center's north tower -- and forever changed the country.
It has now been 15 years since that moment, since that day: 9/11, when nearly 3,000 lives were lost in the nation`s deadliest terrorist attack.
Thousands gathered on the World Trade Center site in lower Manhattan to listen as family members read the names of the victims for nearly three hours.
At the Pentagon, where American Airlines flight 77 crashed, President Obama laid a wreath and paid tribute to the 184 victims who died there.
“E Pluribus Unum, out of many, we are one. For we know that our diversity, our patchwork heritage is not a weakness, it is still, and always will be one of our greatest strengths,” Obama said.
And in Shanksville, Pennsylvania, in the rural field where United Airlines Flight 93 went down the 40 victims were remembered as the heroes.
And back in New York, firefighters performed a somber changing of the guard at the FDNY memorial wall, where so many first responders are remembered for their actions that day in the shadow of Freedom Tower - a symbol of the resilience.
“May god bless the memory of the loved ones here, and across the country. They remain in our hearts today,” Obama said.