WikiProject United States/Boundaries

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Boundaries of states, counties, and county equivalents in the continental United States ("lower 48" states) plus Alaska and Hawaii

The borders of the United States and those of its political subdivisions are represented by administrative boundary relations. The somewhat-paired tags boundary=administrative and admin_level=* are applied to these relations (and often their member ways, for software compatibility reasons) to indicate their relative level in a political hierarchy. Additionally, border_type=* was and is used inconsistently on land boundaries, largely due to import legacies. However, on maritime borders with specifically-defined values, border_type=* is used consistently.

Renderers typically display these boundaries as dashed or dotted lines and may use boundary relations for other purposes, such as to display state-appropriate highway shields. Geocoders use the boundary relations to identify places and construct full addresses. For debugging purposes, ito! Map has a map of administrative boundaries, color-coded by admin_level=* tags on ways (not relations, unfortunately). This rendering can also be helpful.

This article is a basic tagging guide (U.S. admin_level=2, 4, 6, 7, 8, 10). It discusses tagging practices that either are already in wide use in OSM or have achieved consensus through the proposal process. In the interest of clarity, this article does not discuss novel tagging proposals. There are numerous exceptions to the information below, some of them quite significant, but this article ignores them in order to focus on how to tag new features as they come up. For a more detailed explanation of governmental structures described in this article, see United States admin level and Wikipedia's series on U.S. Political divisions.

Summary

The following table contains generalizations meant to reflect current usage in OSM.

If you don't see an entry corresponding to the kind of boundary=administrative you are trying to map, consult the corresponding section for more details. If the section doesn't say how to tag the boundary either, it could be that similar boundaries have yet to be mapped, or perhaps the community has yet to reach consensus on how to tag them. In that case, try to be consistent with the entries below when mapping, and let the talk-us mailing list know what you come up with. Again, see United States admin level for more detail.

United States admin_level=* values (border_type=* values in parentheses)
4 5 6 7 8 9 10
State or Territory
(state)
N/A County
(county)
Civil township
(township)
Municipality
(city, village)
(village,
neighbourhood)
Neighborhood
(neighbourhood,
district)
Alaska N/A Borough N/A City N/A N/A
California N/A County N/A City
Town
N/A Neighborhood
Connecticut N/A County Town City
Borough
N/A N/A
Florida N/A County N/A* City
Town
Village
N/A N/A
Hawaii N/A County N/A N/A N/A N/A
Illinois N/A County Township
Precinct
City
Village
Town
N/A N/A
Louisiana N/A Parish N/A City
Town
Village
N/A N/A
Maine N/A County Township City
Town
N/A N/A
Massachusetts N/A County N/A City
Town
N/A N/A
Michigan N/A County N/A City N/A N/A
N/A County Township
Charter township
Village N/A N/A
Minnesota N/A County Township
Town
City N/A Neighborhood
New Hampshire N/A County N/A City
Town
Ward N/A
New Jersey N/A County N/A Borough
City
Town
Township
Village
N/A N/A
New York New York City † Borough N/A Community District N/A N/A
N/A County N/A City
Hamlet
N/A N/A
N/A County Town Village N/A N/A
Ohio N/A County Township City
Village
N/A Neighborhood
Pennsylvania N/A County N/A City
Borough/Boro
Township
Town (Bloomsburg)
N/A Neighborhood (Pittsburgh)
Planning Analysis Section (Philadelphia)
Rhode Island N/A N/A
(county)
N/A City
Town
Village N/A
Vermont N/A County N/A City
Town
N/A N/A
Virginia N/A Independent city
(city)
N/A N/A N/A N/A
N/A County N/A Town N/A N/A
Wisconsin N/A County Town City
Village
N/A N/A
District of Columbia ‡ N/A N/A N/A Washington N/A Neighborhood
American Samoa N/A District County Village N/A N/A
Guam N/A Village N/A N/A N/A N/A
Northern Mariana Islands N/A Municipality N/A N/A N/A N/A
Puerto Rico N/A Municipio (Municipality) N/A Barrio (Ward) N/A N/A
United States Virgin Islands N/A District N/A Subdistrict N/A N/A
United States Minor Outlying Islands § N/A N/A N/A N/A N/A N/A

National boundary

The United States–Mexico border at San Diego, California, and Tijuana, Baja California

The federal border is represented by Relation 148838 (XML, iD, JOSM, Potlatch2, history, analyze, manage, gpx), tagged boundary=administrative admin_level=2 border_type=national. Where this border delineates U.S. territorial waters (e.g., 12 nautical miles off the Atlantic coast, or surrounding minor outlying islands), the member way is tagged border_type=territorial maritime=yes. State and territorial boundary relations are members of this national boundary relation with the role subarea.

You may find some renderers (notably Carto/standard), especially at very wide (global) zoom levels, display certain members of this relation (Alaska's westernmost Aleutian Islands, Guam and Northern Mariana Islands, Wake Island) in a seemingly inconsistent or unusual manner. This is because these areas are west of 180 degrees (the antimeridian): some renderers may require an additional easterly "pan around the globe" to display them.

States in Free Association

The states in Free Association with the USA (Federated States of Micronesia, Marshall Islands and Palau) have national-level admin_level=2 boundary=administratives of their own and are excluded from the United States' national boundary relation. This is because they are sovereign nations in a Compact of Free Association with the United States.

States and Territories

Main article: United States State Boundary Relations (large table of state and territory relation links).

An Arizona welcome sign at the border with New Mexico

The borders of states and Territories (including Commonwealths) are tagged boundary=administrative admin_level=4. Some states are additionally tagged border_type=state. As noted below, while the District of Columbia does have an admin_level=4 tag, it is not tagged border_type=state.

Where the border delineates state territorial waters (e.g., 3 nautical miles off the Atlantic coast), the member way is tagged border_type=state maritime=yes. Generally, borders along waterways follow the thalweg (deepest path along the channel). However, state river borders are more nuanced, especially along the Mississippi River and Ohio River, whose banks have changed significantly over the centuries. Do not expect to be able to "eyeball" a state border along a river using aerial imagery.

Strictly speaking, United States Minor Outlying Islands (USMOI) is not a boundary=administrative, it is a statistical grouping. However, it is convenient, as all eight Pacific islands or island groups plus one (internationally disputed) island in the Caribbean Sea (each of which are territories) are grouped into a single relation. As with the five coastal/ocean states that have boundaries with the Pacific Ocean and the 17 states that have boundaries with the Atlantic Ocean or Gulf of Mexico, each of these islands has U.S. territorial waters as described above, sufficient to delineate the national boundary around USMOI.

Counties, parishes, boroughs, etc.

A sign marking the border between Summit and Medina counties in Ohio

Boundary relations of political subdivisions of U.S. states known as counties (including Louisiana parishes and Alaska boroughs) are tagged boundary=administrative admin_level=6. Some counties are additionally tagged border_type=county. A county boundary relation's name=* tag should include the word "County" (or "Parish" in Louisiana or "Borough" in Alaska). More county boundary data are available for Georgia, Ohio and Wyoming.

The counties of Connecticut [1] are tagged boundary=administrative admin_level=6, as Connecticut has government at this level, though it is limited. However, as Rhode Island has no county-level governments [2], its counties are tagged neither boundary=administrative nor admin_level=6, making Rhode Island counties geographical subdivisions only [3]. Similarly, in Massachusetts, eight of 14 counties have no county-level government and so also have neither boundary=administrative nor admin_level=6 tags on those eight counties.

County boundaries come from USGS data, which are accurate but have lower resolution than other data in OSM.

Outside of the fifty states, and as each of these are "territorial municipalities": districts of U.S. Virgin Islands, municipios of Puerto Rico, villages of Guam, districts and unorganized atolls of American Samoa [4] and islands and an island group in Northern Mariana Islands are tagged admin_level=6, the same as counties in 49 of the 50 states. (Recall Rhode Island counties are not tagged with admin_level=*). Puerto Rico's municipios and wards were imported from Puerto Rico Planning Board data, while Guam's village data (names end in "Municipality") are from the Census Bureau. A territorial municipality boundary relation's name=* tag should include the word "Municipality" (or one of its flavors: district, municipio, village, unorganized atoll, island or island group).

Civil townships

Welcome sign at the border of Meridian Charter Township, Ingham County, Michigan. Note that townships and municipalities sometimes place welcome signs at the entrance to business districts rather than their borders.

The Census Bureau infers that Civil townships exist as administrative subdivisions in 20 states. They are usually known as townships or towns (sometimes charter townships in Michigan) and are characterized by the fact that they completely subdivide counties (admin_level=6). Hence, civil townships of this kind (including those named "towns") are always tagged boundary=administrative admin_level=7. Depending on the state, it may be possible for a city or village to subordinate to one or more townships, or for a city or village to withdraw from a township, becoming a direct county subdivision. A civil township boundary relation's name=* tag should be prefixed with "Township of" (or "Town of" or "Charter Township of") or suffixed with "Township" (or "Town").

Some states (New Hampshire, New Jersey, Pennsylvania) have administrative subdivisions named "township" but these are not "civil townships" as described here, these are actually city-like, rather than township-like. While this is admittedly confusing, these should be tagged admin_level=8, not admin_level=7. This decreases the number of states asserted by the Census Bureau (20) by three (to 17) that OSM might agree contain "civil townships." The number 17 might change, as of August 2017, this is a bit fluid.

OSM's TIGER 2005 import omitted minor civil division boundaries, including civil townships. Mappers add them manually, often tracing USGS Topographic Maps, where township boundaries are generally shown as black dashed lines. These maps can be slightly misaligned in places, so it helps to switch back to aerial photography once in awhile as a sanity check. If you know the general vicinity of a township line, you may be able to spot a change in pavement quality where one township repaved its road up to the township line.

As mentioned above, except for maritime borders, border_type=* tags suffer from inconsistent application due to legacy imports. Because of this, they might become or are becoming deprecated on land borders. For what it's worth, you may find border_type=* tagging on townships in several of these 17 states. For example, in Connecticut, New York and Wisconsin, border_type=town tagging is found, while in Indiana, Kansas, Maine, Michigan and Ohio border_type=township tags exist (additionally, border_type=charter_township is found in Michigan).

Municipalities

Main article: United States municipalities

A sign marking a municipality boundary, Schulenburg's city limit, Texas

Municipalities are known by many names, such as city, town, township (be careful, see Civil townships above), village, and hamlet. Especially as it is known in the fifty states as "incorporated," tag a municipality with boundary=administrative admin_level=8 and perhaps an appropriate border_type=* tag, such as border_type=city. In rare cases, an unincorporated community may have well-defined borders that justify a polygon or boundary relation tagged boundary=administrative, but it usually suffices to tag these with a place=* node.

A consolidated city-county is mapped as two separate, coterminous boundaries, one for the city (admin_level=8) and the other for the county (admin_level=6). On the other hand, an independent city — that is, a city independent of any county — should be mapped as a single boundary=administrative admin_level=6 perhaps also tagged border_type=city.

Municipal boundaries were imported from TIGER 2005 shapefile data, which is often very high resolution but contains many inaccuracies. The USGS Topographic Maps layer may be a useful resource for realigning municipal boundaries. However, the distinction between municipal boundaries and civil township boundaries on these USGS maps is not always clear. And unlike civil townships, municipal boundaries are far more likely to change over time due to annexation, so a USGS layer may be outdated with respect to city limits.

See the section "Counties, parishes, boroughs, etc." for information on municipalities or municipios in U.S. territories, which are not equivalent to municipalities in states. These "territorial municipalities," which go by several different names, are always admin_level=6, never admin_level=8.

Municipal subdivisions

An entrance to Columbus, Ohio's Forest Park neighborhood

Medium and large cities may have formal subdivisions, variously called neighborhoods, districts, boroughs or wards. Where these subdivisions serve as a system of general-purpose units of government with well-defined boundaries, they are tagged boundary=administrative admin_level=10. In some cities, these subdivisions may correspond to voting districts, but this is not necessarily always true. In cities which contain both wards and neighborhoods, it may make sense to tag the wards admin_level=9 and the neighborhoods admin_level=10, to preserve this hierarchy.

For example, each neighborhood of Cincinnati, Ohio, has a semiformal neighborhood council, and the neighborhood boundaries are well-known. By contrast, many of the neighborhoods of San Jose, California, are amorphous, so they are instead mapped as place=suburb nodes. Naturally, there is much gray area between these extremes, so use common sense. If boundaries of a neighborhood are subjective and impossible to verify using signage alone, chances are the neighborhood is better mapped as a node. Especially when tagged as nodes, such smaller, named place=*s or populated areas inside of larger cities have a distinct method of tagging (e.g. place=suburb, place=quarter, place=neighbourhood...): see place=* for details.

Examples of cities with formal subdivisions include Chicago, Illinois; Cincinnati, Ohio; Cleveland, Ohio; Minneapolis, Minnesota; Seattle, Washington and Washington, D.C.

In smaller cities, especially suburbs, consider mapping (sometimes homeowner association–managed) residential subdivisions with landuse=residential ways (often closed polygons). If there is no particular management but there is a clearly named or signed identity to a residential subdivision, a landuse=residential tag on ways (often closed polygons), plus a name=* tag suffices. (Omit admin_level=*). On the other hand, some planned communities such as The Woodlands, Texas, have a formal system of named subdivisions, which are mapped with type=boundary relations.

Notable exceptions

Other types of boundaries

Other uses of admin_level

The admin_level=* values described above also apply to the following tags:

  • capital=* – A state capital is tagged capital=4, and a county seat is tagged capital=6.
  • heritage=* – For example, a National Historic Landmark is tagged heritage=2, signifying that its historical status is registered with the national-level National Register of Historic Places.