Frontier America consists of sparsely populated areas that are isolated from population centers and services.

Definitions of frontier for specific state and federal programs vary depending on the purpose of the project being funded. Some of the issues that may be considered in classifying an area as frontier include population density, distance from a population center or specific service, travel time to reach a population center or service, functional association with other places, availability of paved roads, and seasonal changes in access to services. Frontier may be defined at the county level, by ZIP code or by census tract.

Frontier, like rural, suburban, or urban, is a term intended to categorize a portion of the population spectrum. Frontier refers to the most remote end of that continuum. For the purpose of defining Frontier for State and Federal programs, the National Rural Health Association recommends that a variety of methodologies be available from which to choose. This will ensure that a program selects the most appropriate designation to suit its purpose, while reducing the likelihood that a program be forced into a definition that does not fit. The following methodologies are indicative of the diversity of frontier definitions employed at the federal level, primarily within the Health Resources and Services Administration.

Rural-Urban Commuting Areas: RUCAs can be used to identify very remote areas, which could be considered frontier-like due to their isolation from population centers. Under the RUCA definition, areas are categorized based on measures of urbanization, population density, and daily work commuting. For instance, a RUCA code of “10” is assigned to isolated, small rural census tracts and may be considered frontier. RUCAs are available by census tract and by ZIP code area. RUCA Version 2 uses 2000 Census data and 2004 ZIP code areas. RUCAs were first introduced in a 1999 article by Richard Morrill, John Cromartie, and Gary Hart - "Metropolitan, Urban, and Rural Commuting Areas: Toward a Better Depiction of the United States Settlement System." Urban Geography 20: 727-748. More information is available at http://depts.washington.edu/uwruca.

Frontier Education Center Composite Designation of Frontier Counties: The National Center for Frontier Communities, in collaboration with the NRHA in 1997, brought together a multi-disciplinary group of experts as a consensus group that developed a frontier matrix for determining frontier status. This methodology was based on population density, distance to the closest "market" for services, and travel time. The consensus group created a typoplogy in which density of counties was coded <12, 12-16, 16-20 persons per square mile. Distance to a service/market was coded >90, 60-90, 30-60, <30 miles. Travel time to service/market was coded >90, 60-90, 30-60 and <30 minutes. This final definition was developed to be inclusive of extremes of distance, isolation, and population density. The definition also reflected an underlying concern that the real frontier dilemma is how to create or maintain even a fragile infrastructure in a frontier community. http://www.frontierus.org/defining.htm

Frontier Areas for Community Health Center Purposes: In 1986, the predecessor to the Bureau of Primary Health Care adopted the frontier county definition which had been developed by the Bureau of Health Professions and legislatively mandated for certain BHPr programs, i.e., to consider as frontier those counties with a population less than or equal to 6 persons per square mile, but added the condition that in order to receive a frontier preference in funding CHCs in such counties should also be located at considerable distance (greater than 60 minutes travel time) to a medical facility large enough to be able to perform a caesarian section delivery or handle a patient having a cardiac arrest. These additional criteria were dropped in later years, and health center programs began to define frontier counties with only the single criterion of population density greater than or equal to 6 persons per square mile. While Bureau of Primary Health Care policies refer to population densities of service areas, densities of counties are often used for analytic and other purposes.

Frontier Extended Stay Clinic: In 2005, with funding from the Health Resources and Services Administration’s Office of Rural Health Policy, the FESC program was created. Eligible facilities are defined as clinics located greater than 75 miles from a CAH or hospital, or inaccessible via public road. More information is available at: http://www.alaskafesc.org.

Telehealth Designation: In 2006, with funding from the Health Resources and Services Administration's Office for the Advancement of Telehealth, an expert panel developed a new frontier area definition that could be applied to telehealth programs. The recommended frontier area definition from the panel is: "ZIP code areas whose calculated population centers are more than 60 minutes or 60 miles along the fastest paved road trip to a short-term non federal general hospital of 75 beds or more, and are not part of a large rural town with a concentration of over 20,000 population."