Those vanishing areas of dark blue are what Obamacare's effect on the number of Americans without health insurance looks like.

The United States Census Bureau on Tuesday released a series of maps that vividly show broad increases in health coverage nationally in the years after full implementation of the Affordable Care Act.

The maps use dark blue to show states that have 14 percent or more of their residents without health insurance. Lighter shades of blue highlight states with lower uninsured rates.

Census officials published the maps as they released a report revealing that the number of Americans who lacked health insurance fell to a low of 28.1 million people, or just 8.8 percent of the population, in 2016. That was the last full year in office for President Barack Obama, who won passage of the Affordable Care Act.

The uninsured rate last year was 0.3 percentage points lower than what it was in 2015 — and almost half of what it was in 2010, the year that Obamacare began taking effect. In 2010, the percentage of people without health insurance stood at 16.3 percent, or a whopping 49 million Americans.

Most states continued to see decreases in their uninsured rates last year, with only 11 states seeing no drop.

But the maps also underscore that the recent gains in health insurance coverage under the ACA have not been consistent nationally.

Those gains were most dramatic in states that as allowed by the ACA expanded eligibility for their residents' access to Medicaid, the health coverage program for mainly poor people that is jointly run with the federal government.

The uninsured rate among so-called expansion states was just 6.5 percent in 2016, Census officials said.

In those states, all legal residents whose incomes are less than 138 percent of the federal poverty rate are eligible to enroll in Medicaid.

But in states that did not expand Medicaid, the uninsured rate was 11.7 percent last year.