"Medicaid is a vital source of health coverage nationwide, but the program’s role is even more pronounced in small towns and rural areas, the study report says. "Medicaid covers a larger share of non-elderly adults and children in rural and small-town areas than in metropolitan areas; this trend is strongest among children. . . . In 2014-2015, Medicaid provided health coverage for 45 percent of children and 16 percent of adults in small towns and rural areas, compared to 38 percent and 15 percent, respectively, in metropolitan areas."
The findings are especially relevant at a time when Congress is debating the future of the Medicaid expansion under the Patient Protection and Affordable Care Act. The bill passed by the House would end the expansion in 2020; Senate Majority Leader Mitch McConnell has proposed a phase-out through 2023. President Trump said in his campaign that he would not cut Medicaid, but then he supported the House bill.
The study includes an interactive map with county-by-county data. Here's a screenshot of a section of the map focused on Kentucky, highlighting the county in the state with the largest share of adults on Medicaid: