This week President Trump paused in his — justified — victory lap on jobs to attack the ­environmental legacy that in part helped power the nation’s prosperity. He assailed “the past administration’s misguided regulations to better protect the environment” in a speech that went far too far in denigrating the role of rational, incremental environmental regulations in improving American life.

A healthy environment is crucial to a strong economy, especially in our post-industrial age. The coal-powered industrial decades of the 19th and early 20th centuries produced immense wealth but at very high cost in pollution and waste.

Particulate matter blackened the skies of major cities, and agricultural and manufacturing runoff polluted waterways. Alarmed scientists and citizens pushed for regulations to bring down emissions — and technological innovations to make this possible.

Mid-20th-century Americans saw air pollution as a catastrophically dangerous problem, horribly demonstrated by October 1948’s lethal haze over Donora, Pa., that killed nearly 40 people and severely sickened thousands more. At the same time, the smog shrouding Los Angeles seemed to worsen precipitately, hovering for weeks at a time.

While much of the early government response came from state and local ordinances, President Dwight Eisenhower in his 1955 State of the Union address asked Congress to fix air pollution. Legislation was ­introduced, but not until 1963 was a major federal law enacted. Meanwhile, the surgeon general and public health officials had been studying motor vehicle emissions, which had become the real post-World War II culprit in LA and other cities.

In 1970, Congress passed the Clean Air Act Amendments. Progress was far from instantaneous. As regulators tried judiciously to figure out the details, pollution seemed to worsen. Taking up the cudgel, popular culture started portraying a dystopian future that struck audiences as all too real. It was easy to imagine that 1972’s “Soylent Green” was depicting the real New York City, and “Blade Runner” in 1982 depicting the real LA: filthy, degraded, washed in acid rain.

But that describes neither city today, as ambitious young people from all over the world flock to both for their economic opportunities, excitement, street life, culture, recreation and all-around confidence that they and their residents constitute the center of the world.

This turnaround was the product of incremental, rational legislation — far from the eliminate-all-private-cars radicalism pushed by Democrats touting a “Green New Deal.” And that’s why it worked.

Successful cities understand all this well. As Manhattan Institute senior fellow Peter Salins noted decades ago, in a modern economy, a city’s face becomes its fortune. That face must be attractive and welcoming, not ugly and polluted. New Yorkers today take Hudson Bay oysters for granted thanks to technological innovations and, yes, regulations against dumping that Trump was too quick to dismiss.

Although it gets less attention, this principle also holds true in rural areas, such as northern Minnesota and western Montana, where mined-out extractive industries are being replaced with wildlife tourism. Clean rivers, blue skies and abundant fish and game are the new economy’s necessary elements.

If the nation heads backwards on air and water pollution, it will head backwards on the economy. This is well understood not only by citizens and elected officials but by corporate leaders. The administration’s plan, for example, to weaken Obama-era regulations that would double fuel economy requirements for new cars was criticized as untenable and unprofitable by 17 auto manufacturers that supported the stronger standards.

California, backed by the governors of 23 other states, intends to pursue its strategy of writing clean air standards higher than what the Trump administration supports. It’s a smart move. While its cities are far more prosperous today than they were in the polluted 1960s and ’70s, they still rank as among the most-polluted cities by ozone — and this includes the glamorous hubs of LA, San Diego and San Jose.

“We will defend the environment, but we will also defend American sovereignty, American prosperity, and we will defend American jobs,” said Trump. That is precisely what the federal Clean Air and Clean Water acts, bolstered by state and local legislation, accomplished, proving that thoughtful, rational regulation works. The Trump administration would be wise to heed this lesson from the past.

Julia Vitullo-Martin is a Regional Plan Associations senior fellow.