A Metropolitan Statistical Area (MSA) is a federal classification used to identify one or more counties or equivalent areas with a large population core of at least 50,000 people and surrounding communities that are economically and socially integrated with that core. Marion County and its contiguous counties fit this definition, although the counties included in the Indianapolis MSA have changed over time. Each MSA is identified by the name of its central city and state.

The rapid suburbanization of population and economic activity during the 20th century meant that previously separated cities became socially and economically connected to large central cities. Termed a metropolis, this late-20th -century form of urbanization consists of areas of intense social and economic interdependence which encompass the boundaries of one large city (the “central city”) and a number of smaller cities (the “suburbs”).

MSAs were first defined in 1950 and definitions are updated approximately every 10 years. The criteria for identifying the boundaries of an MSA have changed only slightly since then. Currently, the U.S. Office of Management and Budget (OMB) is responsible for those definitions. While OMB states that it is only for statistical purposes, the classification is significant in federal funding formulas, as well as in matters involving federal regulations.

The Indianapolis MSA has grown in population and geographic size since 1950. The table below shows included counties and population for the given years of definition.

Population of Indianapolis MSA, including counties and population for the given years of definition. View Source
Revised May 2021

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