JOHN YANG: For decades, going trick or treating has meant more to children across America than just collecting candy for themselves.

It's also meant collecting nickels, dimes and quarters for Children in Crisis around the world.

Ali Rogin tells us how trick or treat for UNICEF began and how it's changed.

ALI ROGIN: It's one of the most recognizable fundraisers in the country.

WOMAN: My oldest and most significant memory is trick or treating for UNICEF with all of my brothers and sisters.

ALI ROGIN: And a mainstay of Halloween for generations of Americans.

WOMAN: When your doorbell rings and you hear won't you help the children help the children?

ALI ROGIN: Public figures from First Lady's and the Brady Bunch actors to singer Sammy Davis Jr. and supermodel Heidi Klum have taken up to cause.

The little orange boxes were many children's first encounter with giving back.

UNICEF USA President and CEO Michael Nyenhuis was one of them.

MICHAEL NYENHUIS, President and CEO, UNICEF USA: I was a boy growing up in Owatonna, Minnesota, and had my little cardboard box and went door to door and it awakened in me something that said, hey, you know there's a bigger world out there and I can do something about it.

ALI ROGIN: It all began around 1950 When a Philadelphia School teacher and her husband, a Presbyterian minister, got the idea to turn trick or treating into charity.

With the blessings of UNICEF they spread the word and children began collecting loose change in milk cartons.

It was a way to do good during a holiday that for much of its history was about being bad.

Lesley Bannatyne is a historian who has written extensively about Halloween.

LESLEY BANNATYNE, Halloween Historian: During the 20s and 30s and 40s Halloween tricks were getting a little bit more intense became more like vandalism, setting fires breaking windows.

ALI ROGIN: In the 50s, there were PSAs encouraging kids to ask for treats instead of doing tricks.

LESLEY BANNATYNE: A Donald Duck cartoon that came out in 1952 called Trick or Treat that taught kids and adults.

The good and bad ways to trick or treat, do not put fireworks in a treat bag, for example, put candy in there.

But the final and I think most important straw was UNICEF, it became a charitable act, as well as a fun act.

ALI ROGIN: Charitable acts that have never been so important since Nyenhuis.

MICHAEL NYENHUIS: There are actually more children displaced from their homes because of conflict and climate change today than at any time the planet and helping out to trick or treat for UNICEF is a way to do it in a fun way.

ALI ROGIN: And now trick or treat for UNICEF is changing too.

During the pandemic UNICEF discontinued the cardboard boxes.

The campaign is now a month long and digital with online fun razors and print out QR codes for kids and adults alike during the holiday.

MICHAEL NYENHUIS: This is a moment to feel incredibly grateful for what we have for our safety and security.

And out of that gratitude, turn around and help out.

ALI ROGIN: As UNICEF says, putting some meaning in your Halloween.

For PBS News Weekend, I'm Ali Rogin.