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.
The maps' release comes less than two months after an effort to repeal Obamacare failed to pass the Republican-controlled Senate, and as the administration of President Donald Trump continues to criticize the health-care law and slashes support for promoting enrollment in private health plans.
Obamacare was signed into law in 2010, but it only began taking full effect in late 2013, with the opening of government-run insurance marketplaces such as HealthCare.gov, which sell private health plans.
Large parts of the United States were dark blue in 2013, according to the Census maps. Only the northeastern U.S., and some Midwest states were in lighter shades of blue, reflecting their relatively low uninsured rates.
"In 2013, the percentage of people without health insurance coverage for the entire calendar year was 13.4 percent, or 42.0 million," Census said in its report for that year.
But the following year, 2014, saw a dramatic decrease in the dark blue areas of the U.S. as millions of people obtained health coverage, with much of the northern states in the country turning lighter blue, according to Census' maps.
That year was the first in which nearly all Americans were required by Obamacare to have some form of health coverage or be subject to a tax penalty. Census' report for that year showed that 10.4 percent of Americans, or 33 million people, still lacked insurance.
In 2015, large swaths of the western part and southeastern parts of the U.S. became lighter blue, indicating an uninsured rate of less than 10 percent.
That year was the first time that the percentage of all Americans without health coverage fell below 10 percent, to 9.1 percent, or 29 million people.
By 2016, most of the U.S. states had uninsured rates below 10 percent. Only Texas had an uninsured rate above 14 percent, and only three other states — Florida, Georgia and Oklahoma — had uninsured rates of 12 percent or higher.
And most of the country continued to see gains in insurance coverage.
"Between 2015 and 2016, the percentage of people without health insurance coverage at the time of interview decreased in 39 states," the Census report said. "Eleven states and the District of Columbia did not have a statistically significant change in their uninsured rate."
The Census report also said that, "In 2016, private health insurance coverage continued to be more prevalent than government coverage, at 67.5 percent and 37.3 percent, respectively."
Job-based health plans covered almost 56 percent of Americans, followed by 19.4 percent covered by Medicaid, and 16.7 percent covered by Medicare.
Another 16.2 percent of Americans bought private individual health plans, which includes Obamacare plans sold on government exchanges. Military-based health plans covered another 4.6 percent of people.
"Between 2015 and 2016, the rate of Medicare coverage increased by 0.4 percentage points to cover 16.7 percent of people for part or all of 2016 (up from 16.3 percent in 2015)," Census said in its report. "There was no statistically significant difference between 2015 and 2016 for any other subtype of health insurance."
White Americans continued to have the lowest uninsured rates by race, at just 6.3 percent.
"The uninsured rates for Blacks and Asians were higher than for non-Hispanic Whites, at 10.5 percent and 7.6 percent, respectively," Census said.
"Hispanics had the highest uninsured rate, at 16.0 percent," according to the report.