Across the country, the day will be marked by formal events such as public readings of victims' names, wreath-laying ceremonies and charity fundraisers. People will donate blood, fly American flags, attend religious services and take baked goods to firehouses. They will spend extra time with family, give money to charity and volunteer at soup kitchens.

Nearly half of Americans plan to observe this anniversary in an informal way, such as saying a prayer or taking a moment of silence, according to a new American Pulse survey by USA Today. Thirteen percent will do it in a more formal manner such as attending a memorial service.