Thursday (Sept. 11, 2014) marks the thirteenth anniversary of the 9/11 terrorist attacks -- a series of events which forever changed not only America, but the world.

On that tragic day, 2,753 people lost their lives during the attacks on New York City's Twin Towers. Firefighters, police officers and Port Authority officers were among those who were killed. There were 343 NYC firefighters, 23 NYC police officers and 37 Port Authority officers lost that day, in addition to 184 killed at the Pentagon.

As everyone reflects today, country stars took to Twitter to remind us to never forget Sept. 11: