The support shown on major landmarks around the world inspired others to create their own tributes. Dan O'Sullivan, a photographer in Colorado, enlisted the help of hiker Sam Chambers to climb the Manitou Incline with colored light panels so he could create a breathtaking composite image in tribute.
"The idea for the image came to me late Friday night when the full scale of what happened was becoming clear and when the first tribute in lights I had seen was the spire on One World Trade," O'Sullivan explained to ABC. "I wanted to add emphasis that terror attack victims and their fellow citizens are in the thoughts of people all around the world. I wanted it to not be only the big cities with iconic structures and built in lights but also iconic locations which could be still be lit with a bit of effort and time."
The Associated Press contributed to this report.