Many geospatial professionals have probably heard or used the acronym “MCD.” It is typically used as a synonym for cities, villages, and towns. However, this is not quite correct.
The acronym MCD stands for Minor Civil Division. The term was created by the US Census Bureau to refer to governmental and administrative subdivisions of counties. MCDs exist in only about half of the states. The Census Bureau uses other county subdivisions in states where there are no MCDs.
In Wisconsin MCDs are equivalent to towns. In Wisconsin, towns are legally established and have some governmental authority.
Cities and villages are also legally established but are not MCDs. The Census Bureau refers to these as incorporated places. Cities and villages are the two kinds of incorporated places in Wisconsin. Other states may have additional legal names for incorporated places.
The Census Bureau links below have some additional definitions that help to clarify these points. It can be confusing however since there is so much variability across the country in terms of the names of MCDs, their legal standing, whether or not they have a function, and how they interact legally with incorporated places and counties.
https://www.census.gov/popest/about/geo/terms.html
https://www.census.gov/geo/reference/gtc/gtc_cousub.html
Here are some notes from these Census Bureau links that give a little more information on MCDs and incoporated places:
Minor Civil Divisions. Minor Civil Divisions (MCDs) are the primary governmental or administrative divisions of a county or county equivalents (such as parishes in Louisiana) in many states. MCDs are legally defined county subdivisions. They comprise both governmentally functioning entities with elected or appointed officials as well as nonfunctioning entities that exist primarily for administrative purposes, such as election districts.
The Census Bureau recognizes MCDs in 29 states, Puerto Rico, and the Island Areas. MCDs include areas designated as barrios, barrios-pueblo, boroughs, charter townships, commissioner districts, election districts, election precincts, gores, grants, locations, magisterial districts, parish governing authority districts, plantations, purchases, reservations, supervisor’s districts, towns, and townships. The District of Columbia has no primary divisions and is considered equivalent to an MCD for statistical purposes by the Census Bureau. MCDs are commonly known as towns in New England, New York, and Wisconsin.
MCDs function as governmental units in all or part of only twenty states (including Wisconsin). Within these twenty states, the Census Bureau produces estimates for all governmentally functioning MCDs and for nonfunctioning MCDs in counties that contain at least one functioning MCD. The legal powers and functions of MCDs within these states are variable. Most of the MCDs in twelve states (Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Wisconsin) serve as general-purpose local governments. In the remaining eight states (Illinois, Indiana, Kansas, Missouri, Nebraska, North Dakota, Ohio, and South Dakota) the MCDs, for the most part, perform less of a governmental role and are less well known locally, even though they are active governmental units.
In states where there are no legally established MCDs the Census Bureau may designate Census County Divisions (CCDs) for statistical purposes.
Incorporated Places. Across the US incorporated places include cities, towns (except in New England, New York, and Wisconsin where the Census Bureau recognizes towns as MCDs for census purposes), boroughs (except in Alaska, where the Census Bureau recognizes boroughs as equivalents of counties, and New York, where the Census Bureau recognizes the five boroughs that constitute New York City as MCDs), villages, and other lesser known identifiers. Incorporated places can cross both county and MCD boundaries.
In some states, all or some incorporated places are not part of any MCD; these places are termed independent places. In nine states—Maine, Massachusetts, New Hampshire, New Jersey, North Dakota, Pennsylvania, Rhode Island, South Dakota, and Wisconsin—all incorporated places are independent places. In other states, incorporated places are part of, or dependent within, the MCDs in which they are located, or the pattern is mixed—some incorporated places are independent of MCDs and others are included within one or more MCDs.