Three years after the Affordable Care Act’s coverage expansion took effect, the number of Americans without health insurance fell to 28.1 million in 2016, down from 29 million in 2015, according to a federal report released Tuesday.

The latest numbers from the U.S. Census Bureau showed the nation’s uninsured rate dropped to 8.8 percent. It had been 9.1 percent in 2015.

Both the overall number of uninsured and the percentage are record lows.

The latest figures from the Census Bureau effectively close the book on President Barack Obama’s record on lowering the number of uninsured. He made that a linchpin of his 2008 campaign, and his administration’s effort to overhaul the nation’s health system through the ACA focused on expanding coverage.

When Obama took office in 2009, during the worst economic recession since the Great Depression, more than 50 million Americans were uninsured, or nearly 17 percent of the population.

The number of uninsured has fallen from 42 million in 2013 — before the ACA in 2014 allowed states to expand Medicaid, the federal-state program that provides coverage to low-income people, and provided federal subsidies to help lower- and middle-income Americans buy coverage on the insurance marketplaces. The decline also reflected the improving economy, which has put more Americans in jobs that offer health coverage.

The dramatic drop in the uninsured over the past few years played a major role in the congressional debate over the summer about whether to replace the 2010 health law. Advocates pleaded with the Republican-controlled Congress not to take steps to reverse the gains in coverage.

The Census numbers are considered the gold standard for tracking who has insurance because the survey samples are so large.

The uninsured rate has fallen in all 50 states and the District of Columbia since 2013, although the rate has been lower among the 31 states that expanded Medicaid as part of the health law. The lowest uninsured rate last year was 2.5 percent in Massachusetts and the highest was 16.6 percent in Texas, the Census Bureau said. States that expanded Medicaid had an average uninsured rate of 6.5 percent compared with an 11.7 percent average among states that did not expand, the Census Bureau reported.

More than half of Americans — 55.7 percent — get health insurance through their jobs. But government coverage is becoming more common. Medicaid now covers more than 19 percent of the population and Medicare nearly 17 percent.