GEOFF BENNETT: Before the United States was founded, the spirit of volunteering was already taking hold in the colonies.

Today, Americans give more of their time than citizens of any other country.

During this National Volunteer Month, our Judy Woodruff set out to explore how this tradition started and why it remains such a defining part of the nation's identity.

It's part of her series America at a Crossroads.

JUDY WOODRUFF: The Patagonia all-volunteer fire department has been a fixture of this small Arizona border town for 102 years.

Its firefighters cover 333 miles of surrounding land, fighting every fire that comes their way, while also providing vital emergency medical services to the largely rural mining and ranching community.

ZAY HARTIGAN, Chief, Patagonia Volunteer Fire and Rescue: I think you find a lot of volunteers, just they look and they say, someone ought to do that.

And then they say, well, I'm someone.

I'm going to do it.

JUDY WOODRUFF: Zay Hartigan is the fire chief here... ZAY HARTIGAN: Just the jacket here is a pretty heavy item.

JUDY WOODRUFF: ... overseeing 35 other volunteers who are following what it turns out is a long American tradition.

In 1736, founding father Benjamin Franklin established the first formally organized volunteer fire brigade in the colonies.

The Union Fire Company in Philadelphia had 26 members and would become a model for how fires in the new nation would be fought.

Today, at least 65 percent of firefighters in the United States are still volunteers.

ELISABETH CLEMENS, University of Chicago: Rates of volunteering are... JUDY WOODRUFF: Elisabeth Clemens of the University of Chicago studies the roots of volunteerism and the way volunteer groups organize.

We spoke at another hub for volunteers in the warehouse of the Community Food Bank in Tucson.

ELISABETH CLEMENS: When we think about volunteerism, we think about well-meaning individuals who give freely of their time and money.

And that's absolutely important.

But what it misses is the extent to which the sort of governance of American society was done by these groups.

These groups become powerful and critical.

JUDY WOODRUFF: What was it about the founding of the country that left it important for American citizens to come up with some of these structures that would get the country up and running?

ELISABETH CLEMENS: Well, there wasn't much there, right?

There wasn't much government.

And to have a revolution to establish a government is done by committees, some of which look very voluntary.

So this idea that you can do public action, whether it's responding to a natural disaster or supporting an ally in war, that you don't have to wait for government to do it.

NATALIE JAYROE, CEO, Community Food Bank: We could not do what we do without our volunteers.

JUDY WOODRUFF: Natalie Jayroe is the CEO of the Tucson community food bank, which, on the day we visited, served 1, 621 people with emergency food boxes.

WOMAN: Thank you.

JUDY WOODRUFF: What would it mean if these individuals weren't giving their tonnage to this place?

NATALIE JAYROE: A lot more people would be hungry; 80 percent of everything that comes into a food bank comes from private sources, and that's private donations, that's food from manufacturers, retailers, but that's also all the labor that our volunteers give us on an everyday basis.

JUDY WOODRUFF: It's an idea that Clemens says differs from the European countries our founders left behind.

ELISABETH CLEMENS: In American political development, there is a suspicion, I think, of government doing too much, and so we have been more reliant on ways of providing public goods that don't look like government, even if there's a fair amount of government hidden in them.

PEDRO TADEO, Volunteer, Community Food Bank: I just like helping people.

MADDOX THOMPSON, Volunteer, Community Food Bank: Everyone's not always going to be as fortunate as others, so being able to come out here for a few hours a day and kind of just help other people out just brings me a little glow in life, a little light.

LINDA PETERSEN-VARGAS, Volunteer, Community Food Bank: We're all part of a community.

We should be helping each other out and doing what we can to help our neighbors.

TOM HUGHES, Volunteer, Community Food Bank: think it's just a national trait that we do this.

Yes, it's unselfish.

JUDY WOODRUFF: All told, last year, volunteers here donated more than 100,000 hours of their time.

That's equal to the work of nearly 50 full-time paid employees.

TIMOTHY SHRIVER, Chairman of the Board, Special Olympics: What great volunteer organizations do is remind you that you can make a difference and you do matter and we need you.

JUDY WOODRUFF: Brothers Tim and Mark Shriver have both harnessed the power of volunteers in their work at international organizations like the Special Olympics and Save the Children.

MARK SHRIVER, Board of Directors, Special Olympics: People want to get involved.

I mean, human beings are social animals, right?

We want to be together.

We want to do something that's good for the community, good for your neighborhood.

JUDY WOODRUFF: They say they learned about the value and power of service from their parents, Sargent and Eunice Kennedy Shriver.

Sargent Shriver founded the Peace Corps and then pivoted to fight President Lyndon Johnson's war on poverty, creating programs like Head Start and VISTA... NARRATOR: America needs VISTA volunteers.

JUDY WOODRUFF: ... or Volunteers in Service to America.

He wrote about it all in a new posthumously published memoir, "We Called It a War."

TIMOTHY SHRIVER: Daddy was a trained lawyer, and he was a political realist and he was very tough-minded.

But he also paid a lot of attention to our mom.

And she believed as much in the goodness of volunteers.

She -- while he was building Head Start, she was building the Special Olympics movement.

So our mom was always telling him, those scholars you like, Sarge, from Harvard and Yale, don't forget the teenagers.

Don't forget the moms.

JUDY WOODRUFF: Did you hear these conversations?

TIMOTHY SHRIVER: I heard that conversation.

He didn't want a Democratic war on poverty.

He wanted an American commitment to ending poverty.

He knocked on as many doors of Republican members of Congress and the Senate as he did of Democrats.

JUDY WOODRUFF: Back in Patagonia, as in many other small and mid-sized communities across the country, volunteer fire crews save the local government money.

Nationwide, the time donated by volunteer firefighters adds up to almost $50 billion a year.

This is a big responsibility you're taking on.

It's dangerous, and yet people still want to do it and not be paid for it.

ZAY HARTIGAN: I think there's a certain pride in just stepping up and filling a need and not putting a price on it.

It's priceless.

JUDY WOODRUFF: Volunteers in this department come to the job from all different backgrounds.

But for Dan Goff and Annette Walker, their reasons for volunteering are the same.

ANNETTE WALKER, EMT, Patagonia Volunteer Fire and Rescue: This town has been very gracious to us, very gracious.

JUDY WOODRUFF: How has this town been good to you?

ANNETTE WALKER: My kids, my husband - - I said it -- a couple years ago, totally lost everything.

And then this department gave them something to do, and then I joined in right after.

It was my way to give back to our town, who stood by us the entire time.

DAN GOFF, EMT, Patagonia Volunteer Fire and Rescue: I will be up front with you.

And I know there's a stigma to this.

I'm actually a heroin addict in recovery, and being of service is sort of part of that recovery.

So it helps me with my -- tackling my addictions and helping the community.

JUDY WOODRUFF: Wow.

That's really powerful to hear.

DAN GOFF: I got Narcan, an apartment, and was able to help people who were in a situation like I was in the past.

JUDY WOODRUFF: So you're able to pay back.

DAN GOFF: Absolutely, and it feels great.

JUDY WOODRUFF: And from one of Patagonia's longest-serving firefighters, Richard Connolly: RICHARD CONNOLLY, Volunteer, Patagonia Volunteer Fire and Rescue: I think that's part of the United States is volunteering and helping others.

And to keep that tradition going and make it even stronger, the more we can do, the better.

JUDY WOODRUFF: For the "PBS News Hour," I'm Judy Woodruff in Patagonia, Arizona.