9/11 was a day of great tragedy. But it also brought out the best in many people. From the crowds who lined up to donate blood, to the police and firefighters who searched through the rubble for survivors, to the people who welcomed displaced families into their homes and comforted victims’ loved ones, the days following 9/11 were filled with countless acts of heroism.

Amongst the greatest of those heroes were the emergency service workers who dove in to the eye of the storm, despite the great danger, and risked their own lives to save others. Now, in commemoration of the 10th anniversary of 9/11, DoSomething.org is giving young people across the country the opportunity to honor emergency service workers – both past and present.

The campaign, called Decade of Thanks, will run through September 18. People can get involved in three ways: they can leave their message online, text “DECADE” to 38383, or print out letters to hand deliver to nearby hospitals, fire departments, police stations, or other locations. The messages are all being compiled into a “gratitude map,” that showcases the swelling feelings of thanks felt towards emergency service workers nationwide.

More than 1,500 people have already registered their thanks (the goal is to reach 10,000 messages). Find out how you can share your own gratitude here.