President Barack Obama has declared this weekend, Sept. 9-11, as National Days of Prayer and Remembrance.
"I ask that the people of the United States honor and remember the victims of September 11, 2001, and their loved ones through prayer, contemplation, memorial services, the visiting of memorials, the ringing of bells, evening candlelight remembrance vigils, and other appropriate ceremonies and activities," Obama said in a proclamation statement released by the White House.
As the nation prepares to commemorate and honor the lives lost in the horrific terrorists attacks, Obama said Americans must "never forget that day" and should continue to "draw inspiration from the survivors who still bear the scars -- both seen and unseen -- of that tragic day."
He asked his fellow citizens to use these days to "reflect on the freedom and tolerance that define this great nation."
Republican presidential nominee Donald Trump and Democratic nominee Hillary Clinton have both agreed to stop all TV advertising to mark the 15th anniversary of the attacks.
Meanwhile, House Speaker Paul Ryan joined members of the House on the steps of the Capitol for a remembrance ceremony.
"We lived through that terribly day," Speaker Ryan said surrounded by members of Congress. "We will never forget that terrible day."
Ryan and other politicians honored the heroism of first responders and those who valiantly attempted to save their fellow countrymen.
"I think of the firefighters, the people who went rushing into danger when the whole world was running away from," Ryan said. "These are the stories that we can pass on. We can turn our burden of grief to a gift of grace."
Scores of events are being planned around the country to pay tribute to the victims of the attacks.