There are over 3,000 counties in America. Many are microcosms of how the very rich and very poor live. Others are examples of places where natural resources are abundant. Some counties are as small as a few square miles. Others are huge, like some of those in Wyoming. Some are parts of cities that have dense populations. Others, particularly in states like Alaska, are sparsely populated. But the worst county to live in America is Todd County, South Dakota.

While there are countless factors (many of them subjective) that can contribute to or detract from quality of life, there are a few key objective measures that can reveal a great deal about a given area. The United Nations Development Programme identified some of these measures and created the Human Development Index, a tool to gauge and compare prosperity at a national level from a holistic perspective.

Inspired by the HDI, 24/7 Wall St. created an index of three measures — poverty, life expectancy at birth, and bachelor’s degree attainment — to identify the 50 worst U.S. counties to live in. And here is the worst city to live in every state.

The three measures used to pick the worst counties to live in are closely related to each other. People living in poverty often are less able to afford health care or healthy lifestyle choices, both of which can have serious health repercussions. Similarly, higher educational attainment has been shown to improve health outcomes and reduce the likelihood of unemployment and financial hardship. Both high poverty rates and low educational attainment rates are common in parts of the United States with low life expectancy at birth. 

Many of the counties on this list are in rural Appalachian coal country, an area that has been economically decimated by the decline of coal mining in the United States. Once an economic pillar in communities across West Virginia and Kentucky, coal production has declined precipitously in these areas as the U.S. power grid moves away from coal and relies more on cleaner-burning natural gas and renewable energy sources.

Other counties among the worst to live in are located in or around American Indian reservations. Due to a number of historical and contemporary factors, including their historical mistreatment by the U.S. government, Native American populations are among the most disadvantaged in the United States. Native Americans commonly face generational poverty resulting, and certain existing conditions in some reservations also affect upward economic mobility. For example, reservation land is often communally owned, making it difficult for local residents to build wealth through homeownership.

Todd County, the worst county to live in America, covers part of the Rosebud Indian Reservation, along South Dakota’s southern border. These are the county’s measures:

Poverty rate: 55.5%

Adults with a bachelor’s degree: 15.6%

Life expectancy at birth: 66.7 years

Total population: 10,195

Largest place in county: Rosebud

The county ranks as the worst place to live in the country in part because it is the poorest place in the country. An estimated 55.5% of the local population live below the poverty line, more than four times the national poverty rate of 13.4%. Also, most households in the area earn less than $25,000 a year. Here is the county in every state where the most people live below the poverty line.

As is the case in most poor areas in the U.S., public health outcomes are also below average in Todd County. Average life expectancy at birth in the county is just 66.7 years — more than 12 years below the national average. While poverty contributes to poor health outcomes in the area, so do unhealthy behaviors. For example, smoking is the leading cause of preventable death in the United States, and in Todd County, 41.5% of adults smoke, the largest share of any U.S. county.

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