168 people were killed on April 19, 1995 when an explosion ripped through the Alfred P. Murrah Federal Building.
Survivors and family members fell silent for 168 seconds to honor each of the lives lost.
Oklahomans vowed they would never forget the tragic day and they gather each year to pay tribute to the victims.
Two former American soldiers associated with an extreme right wing and militant group were charged for the home-grown terror attack.
Timothy McVeigh and Terry Nichols were convicted for their role in the bombing.
McVeigh was eventually executed.