The 50th anniversary of the Clean Water Act was celebrated Friday on the East Boston waterfront, where public officials and school children gathered to reflect on the federal law that led to five decades of improvement to the city’s harbor.

The landmark law is widely credited with transforming Boston Harbor from a wasteland of raw sewage and untreated industrial waste into one of the nation’s most improved waterways.

“We dumped waste, we dumped chemicals, all sorts of things into the water,’’ Radhika Fox, the EPA’s assistant administrator for water, said as she stood in Piers Park, the city’s skyline gleaming in sun behind her. “And it wasn’t unusual to Boston Harbor, that is what communities all across the country were like 50 years ago. Rivers ran in color.’’

Passed by Congress in 1972, the act established national wastewater standards and requires polluters to obtain permits before dumping into navigable waters. It aims to make public waters fishable and swimmable.

Fox called that goal the “North Star’’ that guides the agency’s policies across the country. Key to its success is the EPA’s partnerships with local governments and organizations, she said.

Still, despite improvements in water quality overall, Fox said, there are still portions of the country without access to safe water.

She said the Biden administration is committed to improving water quality, highlighting $50 billion earmarked for water infrastructure as part of the Bipartisan Infrastructure Law passed last year.

Mayor Michelle Wu cited national improvements in water quality since the act passed, but said there is still a long way to go.

“We know that communities of color, who tend to have less access to fresh air and clean water, are the residents who stand to lose most,’’ Wu said. “We stand here today united and ready to fight for the next 50 years and beyond.’’

“This is an incredible day, we’re celebrating an incredible victory,’’ Markey said. “We want to be the greenest, cleanest city in the history of the world, and we’re on our way to accomplishing that goal because of the great leadership here.’’

But he also warned that the Clean Water Act is under threat, citing a case pending before the US Supreme Court, Sackett v. EPA, which aims to settle a longstanding dispute over whether the EPA controls wetlands.

The Supreme Court “is poised to roll back protections for the waters of the United States’’ Markey said.

Also in attendance Friday morning were Representative Ayanna Pressley; David Cash, regional administrator for the EPA; Lisa Wieland, CEO of MassPort; Martin Suuberg, commissioner of the Massachusetts Department of Environmental Protection; and Magdalena Ayed, executive director of nonprofit The Harborkeepers.

Students from the nearby Donald McKay K-8 School attended the ceremony for a lesson on public advocacy.

Jordan Huynh, a teacher at McKay, said his students wrote letters to Wu, Markey, and Mariama White-Hammond, the city’s chief of environment, energy, and open space, as part of a lesson on advocacy — “our big vocabulary word,’’ he said.

“We had students talk about advocating for healthy snacks in school, we had students advocate against deportations,’’ Huynh said.

As the ceremony closed, the students swarmed the podium — hand-delivering their letters and holding out notebooks for autographs from Markey and Wu.

Markey, who grew up in Malden, told the class that, when he was in fifth grade, he used to be forbidden from swimming in the nearby Malden River.

“That’s when I began to question environmental policies,’’ Markey said. “You are the leaders, you are who inspire us.’’

Daniel Kool can be reached at daniel.kool@globe.com. Follow him on Twitter @dekool01.