Incomes vary considerably across the country as well as within states. The income gaps between each state’s richest county and poorest county also vary considerably, with some states more equal than others. Still the states’ poorest counties have much in common, and with one exception, median household incomes in all are lower than the national median income. The only exception is the poorest county in Connecticut, where the typical household earns $59,392 annually, more than the $53,889 income of the typical American household.

Loudon County, Virginia is the richest county in the United States, with a median household income of $123,453 a year. McCreary, Kentucky is the poorest U.S. county, with a median household income of $19,328 a year.

To highlight how income levels vary geographically, 24/7 Wall St. reviewed annual median household incomes in every county, in every state.

Click here to see the poorest counties in every state.

Click here to see the richest counties in every state.

Income is one of the principal determinants of well-being, and when income falls below a certain threshold, financial hardship that can affect many areas of life becomes considerably more likely. In low-income areas, poverty is far more common than elsewhere, especially when compared to other, wealthier areas in the state. In all but nine states, the poorest county’s poverty rate is at least double that of the richest county. And in most states, residents of the poorest county are more than three times as likely than residents of the richest county to live in poverty.

Educational attainment is one of the best predictors of future income levels. Compared with state measures and those of nearby rich areas, low-income counties tend to have lower college attainment rates. In only four cases, adults living in a state’s poorest county are more likely to have gone to college than adults nationwide: Madison, Idaho; Jackson, Illinois; Berkshire, Massachusetts; and Whitman, Washington. Incidentally, major colleges or universities operate in the vicinity of these four counties, and in each area there are above average shares of residents currently enrolled in college.

Education levels in rich areas exceed those in poor areas in every state except for Washington and Montana. In a majority of states, the highest income county reports a college attainment rate at least double that of the poorest county.

County population and density also appear related to income levels, as most states’ rich counties are considerably more populated and more dense than the poor counties. Of the 50 low-income counties on this list, all but eight are more sparsely populated than their state’s respective richest county.

To identify the poorest county in each state, 24/7 Wall St. reviewed median annual household incomes from the U.S. Census Bureau’s American Community Survey (ACS). In order to be considered, counties or county-equivalents had to have a population of at least 10,000 people. We also reviewed in each county the percentage of adults who have completed at least high school and at least college, as well as poverty rates, the percentage of owner-occupied housing units (the homeownership rate), median home values, and the percentage of area adults who identify as American Indian or Alaska Native from the ACS. All ACS data are five-year averages for 2011-2015. Unemployment rates are from the Bureau of Labor Statistics and are for November 2016, the most recently available period. Population density came from the Census Bureau’s 2010 decennial census.

These are the poorest counties in each state.