Average life expectancy for Americans can vary by as much as 15 years, depending on where one is born. While the average person born in Montgomery County, Maryland is expected to live for 83.3 years, the life expectancy for a person born in McDowell County, Virginia is just 68.4 years — closer to the life expectancy of India or the Philippines than the United States.

Because health outcomes are the result of several factors — including healthy behavior, access to care, quality of care, socioeconomic factors, genetics, environment and others — Americans’ overall health varies considerably by geography.

32. New York

> Healthiest county: Nassau
> Smoking rate: 11.7%
> Obesity rate: 23.5%
> Median household income: $99,465

Nassau County is located in Long Island, adjacent to the Queens borough of New York City. The healthiest county in New York state, only 11% of county adults report being in fair or poor health, a far smaller share than the 16.2% share of adults statewide.

Residents are also less likely to engage in risky behaviors, which may partially explain positive health outcomes in the county. The incidence of sexually-transmitted disease is frequently used to gauge risky behavior in an area. In Nassau, there are only about 257 new cases of chlamydia annually for every 100,000 residents, about half the corresponding statewide STD rate. The typical adult living in the area is also less likely to smoke or drink excessively than the typical adult in New York state.

To identify the healthiest county in every state, 24/7 Wall St. reviewed county-level health data from County Health Rankings & Roadmaps, a Robert Wood Johnson Foundation and University of Wisconsin Population Health Institute joint program.

The report ranked each state’s counties based on the incidence of premature death and self-reported levels of health — that is, how long and how well residents live.

Premature death rates are measured as the number of people who die before age 75 per 100,000 people annually. Nationwide, the premature mortality rate is 333 deaths per 100,000 people. All but three counties on this list have a lower premature death rate than the national average.

County Health Rankings measures how well residents live based on a number of behavioral metrics, including how active a given population is, the smoking rate, excessive drinking rate, STD diagnosis rate, and obesity rate.

While health outcomes are far worse in some states than others, even in the least healthy states there are counties that are relatively healthy compared to the nation. While the average life expectancy in 66 of the 67 counties in Alabama — one of the least healthy states — is shorter than the average life expectancy nationwide of 78.5 years, in Shelby County, life expectancy is 79.2 years. Such standout counties tend to be home to the wealthiest, most-insured populations in a given state.

Individuals with health insurance are more likely to schedule regular checkups and receive other forms of preventive medical care. All but six counties on this list have a lower uninsured rate than their home state.

Even with insurance, health care and healthy lifestyles can be expensive — and every county on this list has a higher median household income than its respective state. Of the 50 counties on this list, five have a median household income above $100,000 and all have a higher median household income than the $53,889 national value.

To identify the healthiest county in every state, 24/7 Wall St. reviewed county-level data from County Health Rankings & Roadmaps, a Robert Wood Johnson Foundation and University of Wisconsin Population Health Institute joint program. Rankings are based on overall health outcomes — a weighted composite of length of life, quality of life, and maternal health — and overall health factors. The health factors component is itself a weighted composite of health behaviors, clinical care, social and economic factors, and physical environment measures. Data were compiled from more than 20 different sources and are for the most recent year available. A total of 3,140 counties were considered.

Click here to see the healthiest county in every state.