Hard hats are the team headgear of working-class America — the people who built the United States with their bare hands. The people who still build the USA today.

Tip your safety cap to Edward W. Bullard (1893-1963), a U.S. Army veteran who crafted the world's most important piece of industrial protective equipment after returning from the carnage of World War I. 

"Hard-hat workers are brave people doing important work," said Wells Bullard, CEO of E.D. Bullard Co. in Kentucky, a manufacturer of personal safety equipment. She's also a great-granddaughter of the hard-hat inventor. 

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"They are the people building our roads, bridges and infrastructure, moving our economy forward," she added. 

The effort requires a lot of Bullard's hard hats. 

Some 33 million Americans, about 10 percent of the national population, work hard-hat jobs today, according to Cam Mackey, president and CEO of the International Safety Equipment Association. Edward Bullard helped found the nonprofit trade association in 1933.

The hard hat today is more than just an important piece of personal safety equipment. 

It came to symbolize the growing schism between working-class Americans and leftist elitists during the Vietnam War, most notably during the New York City Hard Hat Riot of 1970. 

Construction workers, incensed by images of people burning American flags, walked off their job sites en masse and clashed with largely college-educated, white-collar anti-American protesters in Lower Manhattan. 

About 150 people were battered and bloodied on the streets, 40 of them suffered head wounds, six men were beaten unconscious, David Paul Kuhn, author of "The Hardhat Riot: Nixon, New York City, and the Dawn of the White Working-Class Revolution," told Fox News Digital.

"After that day, the hard hat became a political symbol," he said. 

The nation is still dealing with the fallout today. 

The hard hat carries symbolism far from the job site.

Inspired by doughboy helmet

Edward R. Bullard was born in Liberty, N.M., on Dec. 1, 1893 before moving as a young boy with his family to California. 

His father, Edward D. Bullard, founded the E.D. Bullard Co. in San Francisco in 1898, providing lamps and other gear to miners who flooded the region during the Gold Rush. The company in recent decades moved its operations to Kentucky. 

The younger Bullard graduated from the University of California at Berkeley before shipping off to France in World War I. 

"He was in the trenches in Europe," Wells Bullard said, then returned from war to work at the family business. 

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"Realizing the need for greater safety within the mines, Bullard designed a hard hat for miners inspired by the steel doughboy helmet he wore as a soldier," states a Bullard company biography.

"The helmet was made of canvas, glue and black paint, and given the trademarked name ‘Hard Boiled’ because of the steam used in the manufacturing process," the National Museum of American History reports. 

The Hard Boiled Hat, first developed in 1919, quickly evolved with better designs and safety measures, including webbing to provide a cushion of space between the helmet shell and a worker's head. 

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Bullard applied for a patent for his product in 1927, receiving approval in 1929.

His hard hat soon played a crucial role in some of the nation’s most ambitious — and most dangerous — construction projects. 

The Golden Gate Bridge, built between 1933 and 1937, was the first major construction project to require hard hats on the job — Bullard's hard hats.

He was inspired to help with the project after realizing the deadly danger posed by falling rivets. More than 1.2 million rivets hold together the majestic bridge. 

Any one of them could prove deadly. 

Bullard's hard hat worked. Eleven men died on the project, a horrific figure by today's standards — but the death total was far better than the standards of the day. 

Projections indicated as many as 35 workers would die while building the Golden Gate Bridge, reports Constructors Inc. 

The Hoover Dam and various New Deal projects, such as the Tennessee Valley Authority, also served as proving grounds for the protective equipment. 

Hard hats became mandatory on most job sites with the passage of the Occupational Safety and Health Act (OSHA) in December 1970. The year proved critical in the history of the hard hat.

Hard Hat Riot: Blue-collar America fights back

Hard hats were at the center of America’s culture war in 1970, when blood spilled on the streets of Manhattan. 

Anti-American protests erupted around the nation in the wake of the killing of four Kent State University students on May 4 that year.

New York City protests centered around Wall Street and City Hall in Lower Manhattan. 

"By an accident of history, these protests took place right below one of the greatest concentrations of blue-collar workers in American history," said author Kuhn.

That would be the World Trade Center. 

Some 5,000 hard-hat workers toiled every day in 1970 on the colossal construction project, including its iconic Twin Towers, just blocks from the protests.

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"These workers were more likely [than the protesters] to have kin and colleagues and neighbors in Vietnam," said Kuhn. 

Among other affronts to hard-hat Americans: then-Mayor John Lindsay ordered City Hall flags flown at half-mast after the Kent State killings.

New York City's hard-hat workers had enough. They left the World Trade Center, and other job sites around the city, and descended on downtown Manhattan to take back their country — hard hats resting proudly on their heads.

"The construction workers marched on through the narrow streets of the Financial District toward City Hall, where they sang ‘The Star-Spangled Banner’ and demanded that Mayor Lindsay raise the flags to full-mast," reports Smithsonian Magazine. 

"They eventually got their way." 

The media quickly dubbed it the Hard Hat Riot. The violent scuffle "was the prelude to the divide we now live with in America between the white working class and the highly educated elite," said Kuhn. 

Working-class America rallied for President Richard Nixon during his 1972 re-election bid, helping him win 49 of 50 states and 61% of the popular vote over Democrat George McGovern. 

The "FDR Coalition" of Ivy League elites and blue-collar Americans, Kuhn noted, quickly unraveled in the wake of the Hard Hat Riot.

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"Nixon won the support of nearly six in 10 white labor union members in 1972," he said. "A generation later, they would be called Reagan Democrats. And by the late 1990s, most were Republicans. Most of the last holdovers who stayed Democratic — Trump won in 2016."

Passion for protecting workers 

Edward W. Bullard died on April 18, 1963, at Marin General Hospital after the life-long smoker suffered through a battle with emphysema. He was 69 years old. 

To read more stories in this unique "Meet the American Who…" series from Fox News Digital, click here. 

Bullard is buried today at Cypress Lawn Cemetery in Colma, California, just south of San Francisco. 

"My understanding of Gramps is that he was very humble," said Wells Bullard.

"Just a real open-minded, creative, warm-hearted, very smart person. He had a real passion for protecting workers, for advancing worker safety."

His legacy lives on today in the success of many of the nation’s most ambitious construction projects — and in the daily experience of millions of hard-hat workers from coast to coast. 

Americans purchase about 6 million new construction hard hats each year, according to industry sources.

"As a guy who’s been hit in the head by any number of objects on any number of job sites, let me just take a moment to thank and congratulate Edward Bullard for making a dangerous world just a little bit safer," Mike Rowe, host of "How America Works" on Fox Nation, told Fox News Digital.