President Obama energetically touted the success of the Affordable Care Act on Thursday, saying that an estimated 20 million people have gained health coverage since the law was passed in 2010.

During a trip to Milwaukee, Obama cited a new administration report attributing the increase in the number of insured Americans to provisions that created health insurance marketplaces where consumers can buy private plans, expanded Medicaid, required insurers to cover people with medical conditions and permitted young people to stay on their parents’ health plans until they turned 26.

The president’s trip was designed to reward Milwaukee for its success in signing up people for coverage. It won a competition called the Healthy Communities Challenge that involved 20 cities.

The administration described the drop in uninsured numbers as “historic.” In a statement, Sylvia Mathews Burwell, secretary of health and human services, said, “We have seen progress in the last six years that the country has sought for generations.”

Thursday’s report was an update of an HHS estimate last September, which found that 17.6 million uninsured adults had gained coverage as a result of the ACA. The new findings show that more than 6 million adults ages 19 to 25 have gained insurance under the law. Gains in coverage among previously uninsured adults were strong across all racial and ethnic groups, according to the report.

[The administration makes it harder to get coverage outside regular enrollment period. ]

HHS said the update was designed to focus exclusively on the impact of the ACA and not on other factors, such as the state of the economy, that could have affected whether people gained coverage.

In a separate announcement, HHS said it is ahead of its own schedule in working to shift how Medicare pays for care – from the quantity of tests and services provided beneficiaries to the quality of the care delivered.

Federal health officials had set what they described on Thursday as the “ambitious stretch” goal of having 30 percent of the program’s payments reflect this new approach by the end of this year. They met their goal 11 months early, they announced. In 2014 alone, they said, the result was $411 million in health care savings.

The payment shift is taking place in large part through accountable care organizations and other initiatives established under the ACA. The administration’s next target is for 50 percent of the payments made by Medicare to be based on quality by 2018.

In a media telebriefing on Thursday, Patrick Conway, chief medical officer for HHS’s Centers for Medicare & Medicaid Services, attributed the effort’s success to a combination of factors. Providers are working to deliver care when and where patients most need it, Conway said, to help them stay out of the hospital and to better coordinate the services they receive.