The health care bill proposed in Congress last week would strip coverage from millions of Americans and put insurance costs out of reach for millions more. It would especially harm lower-income workers and older Americans. Like any effort to roll back the gains of the Affordable Care Act rather than build on them, it would do untold damage to the health and financial security of our middle class.

If that isn’t enough reason to oppose it with all our strength, it would also hurt Boston’s economy and cost us jobs.

Health care is a multibillion dollar industry in Greater Boston, a critical component of our vibrant local economy, and a hallmark of our global reputation. Boston’s teaching hospitals alone provide over 66,000 jobs and a direct economic impact of more than $14 billion in our city. That figure multiplies many times over when you add the health centers, private practices, medical schools, research labs, health insurers, and pharmaceutical, medical device, and digital health companies thriving in our city. Health care creates more jobs than any other industry in Boston, by a wide margin. Many of these jobs provide low-income workers their best opportunity to build a career and achieve financial security. Meanwhile, the ACA has helped more than 20 million Americans get health insurance, lifting our national coverage rate to an all-time high of over 91 percent.

The ACA was based on our own 2006 Massachusetts law, passed with bipartisan support in the State House and in strong partnership with our congressional delegation, led at the time by health care champion Senator Ted Kennedy. The ACA was a historic achievement that is now woven not only into our health care system but also our economy. Nowhere is that more true than in Boston, the world’s health care leader.

Boston is poised to move to the next level of health care reform, to continue our progress in improving access and quality while simultaneously reducing costs. But we know that progress requires concerted and thoughtful hard work. That’s not what’s being proposed in Washington.

If the ACA is killed in haste and without an adequate replacement, the gains we’ve made since 2006 would be in jeopardy. It took years to deliver on thoughtful health care reform in Massachusetts and decades to do so at the federal level. Rash and irresponsible action in Washington would cause tremendous instability in Boston’s health care industry, as well as direct harm to the health of our residents, especially the most vulnerable.

We believe the ACA is worth defending and improving. But if Congress and the White House are serious about making dramatic changes to our health care system, it is imperative that these changes not strip our neighbors of lifesaving health care or the jobs that fuel our communities.

We encourage our congressional and state leaders to continue defending our state’s nearly universal coverage. And we call on everyone to raise their voices, share their stories, and hold Washington accountable for protecting the health of our communities and our economy.

Martin J. Walsh is the mayor of Boston. Kate Walsh is the president and CEO of Boston Medical Center.