The counties above are colored based on standard deviation, which measures how much a county’s uninsurance rate is above or below the state average. Purple counties are at least one standard deviation above state average — meaning they have a uniquely high number of uninsured residents — while green counties are at least one standard deviation below.

Of these counties with a significantly high percentage of residents lacking insurance, many feature significant Hispanic populations. Some are centered in major cities with large Latin American neighborhoods, such as Queens County in New York City and Cook County in Chicago, while others are in rural areas with a high proportion of immigrants like southwestern Kansas and Texas’ border with Mexico.

Highly uninsured counties also include isolated Hispanic enclaves in otherwise white-dominated states, such as Nobles County in southern Minnesota, Clark County in eastern Idaho, and Buena Vista County in northwestern Iowa.

Hispanics are among the worst-insured ethnic groups in the U.S., largely because undocumented immigrants — which represent about one quarter of Latinx adults — are ineligible for Medicaid and other government health benefits, according to The Atlantic. Many Hispanics also avoid health insurance due to language barriers, cultural differences and fears of exposing their immigration status.

“When the [Affordable Care Act] was being debated, one of the criticisms that many Republicans made is that it would provide coverage to undocumented people or that it would become a magnet for immigrants coming to the U.S.,” said Sherry Glied, a health economist and dean of New York University’s Wagner school of public policy. “The ACA language is quite clear, and you can’t get into the marketplaces without having to check through Homeland Security that you are legally in the country.”

Across the U.S., Hispanics and Native Americans are the least insured racial and ethnic groups, each more than twice as likely to be uninsured as non-Hispanic whites. As a result, the pattern of Hispanic counties facing above-average uninsurance rates also applies to Native American counties.

Native American counties with significantly high uninsurance rates include Sioux tribal lands in North and South Dakota, Mackinac County on Michigan’s Upper Peninsula, Okanogan County on Washington’s northern border, and McKinley County in western New Mexico.

The prevalence of Native Americans lacking health insurance is largely a result of high rates of poverty, according to the Kaiser Family Foundation.

It is also a result of many Native Americans’ reliance on the Indian Health Service, a government program that funds a network of health centers that provide care without formally requiring insurance. However, although some uninsured Native Americans can be treated at IHS centers, these hospitals and clinics are chronically underfunded and “remain insufficient to meet health care needs,” according to KFF.

“It is important to distinguish [access to the IHS] from having insurance,” Glied said. “It’s not really the same thing. [Insurance] gives you a lot more choice.”

Alongside Hispanics and Native Americans, a third cultural group is strongly correlated with high uninsurance rates. Unlike the others, however, this group is made up almost entirely of non-Hispanic whites, and is not typically considered a marginalized population: the Amish.

Many Amish avoid health insurance for cultural reasons, just as they do for cars and phones. Despite lacking insurance, the Amish have generally good health outcomes, according to data from the University of Wisconsin Population Health Institute.

Although there are relatively few counties with large Amish populations, they represent five of the ten U.S. counties whose uninsurance rates are the most standard deviations above their state averages. These include Holmes County, Ohio, LaGrange County, Ind., and Lancaster County, Pa.