This year, the event was not only solemn but rainy.
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"I say it all the time, I tell my wife, every time it's raining, it's the tears from people, angels looking down on us," said Robert Rutenburg of Holland, Pennsylvania. "It's just traumatic every year."
Rutenburg not only witnessed the tragedy while working in New York City, but he also lost a number of friends.
Nearly 3,000 people died, including 18 victims from Bucks County.
"The same people come and look at the names of the people from Bucks County. I got to know their families," said Sara Webster of Doylestown, Pa.
In Tullytown Borough, Bucks County, the community dedicated a new 9/11 memorial that includes a piece of the World Trade Center and the Pentagon.
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"The memorial is a long time coming. The actual piece of the south tower we have came between 12 and 15 years ago," said Tullytown Borough Fire Marshall David Pearl.
With each passing year and each event, the need to remember is highlighted.
In a moving tribute Sunday night, the crowd lit candles at the Garden of Reflection, signifying light after darkness.
"There are lessons in history. If you don't know your history, if you don't learn from your history, if you don't remember what's important in life -- then you lose your way," said Webster.