The most important numbers are for all Americans under 65, who do not qualify for Medicare. Aleutians East leads with 46 percent uninsured, followed by four Texas counties: Hidalgo, Hudspeth, Presidio and Webb, all between 39 and 36 percent. The data are from 2011, the last year available; data going back to 2006 allow you to check trends among states during those six years. Here is an example of a statewide story, mentioning individual counties.
The data can also be sliced by income levels: less than 138 percent of the federal poverty line, the new eligibility threshold for Medicaid in states that have expanded it; and less than 400 percent of the poverty line, the threshold for subsidies for insurance policies that the exchanges will offer. And you can create your own state-by-state maps, suitable for publication. The Census site is here; the interactive tool is here. To get county data, limit the geography to a state and check the Show Counties box.