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 1. Home
 2. Data
 3. U.S. Maritime Limits & Boundaries


U.S. MARITIME LIMITS & BOUNDARIES

Maritime limits and boundaries for the United States are measured from the
official U.S. baseline, recognized as the low-water line along the coast as
marked on the NOAA nautical charts in accordance with the articles of the Law of
the Sea. The Office of Coast Survey depicts on its nautical charts the
territorial sea (12 nautical miles), contiguous zone (24nm), and exclusive
economic zone (200nm, plus maritime boundaries with adjacent/opposite
countries).

Select limit or boundary for specific information. Data shown is available for
download.

View Larger Map


ACCESS DIGITAL DATA

Static Data Downloads: ESRI shapefile and KML/KMZ

To view ESRI shapefile, you might need ArcGIS Explorer. To view KML, you might
need Google Earth.

Dynamic Map Services

ESRI REST Service

OpenGIS® Web Map Service (WMS)

Dynamic map services are updated whenever we make updates to our data. If you
are using maritime boundaries in a web map or as a background for other data, we
recommend using our dynamic services, as they will seamlessly update in your
application. For information about using dynamic map services, please see the
frequently asked questions page (FAQ).

Metadata: HTML, XML


GENERAL INFORMATION

NOAA is responsible for depicting on its nautical charts the limits of the 12
nautical mile territorial sea, 24 nautical mile contiguous zone, and 200
nautical mile Exclusive Economic Zone (EEZ). These zones are in orange.



Territorial Sea

The territorial sea is a maritime zone over which the United States exercises
sovereignty. Sovereignty extends to the airspace above and to the seabed below
the territorial sea. The U.S. territorial sea extends 12 nautical miles from the
baseline.

Contiguous Zone

The contiguous zone of the United States is a zone contiguous to the territorial
sea. In this zone, the U.S. may exercise the control necessary to prevent and
punish infringement of its customs, fiscal, immigration, cultural heritage, or
sanitary laws and regulations within its territory or territorial sea. The U.S.
contiguous zone is measured 24 nautical miles from the baseline.

Exclusive Economic Zone (EEZ)

The exclusive economic zone (EEZ) of the U.S. extends 200 nautical miles from
the territorial sea baseline and is adjacent to the 12 nm territorial sea of the
U.S., overlapping the 12-24nm contiguous zone. Within the EEZ, the U.S. has:

 * sovereign rights for the purpose of exploring, exploiting, conserving and
   managing natural resources, whether living and nonliving, of the seabed and
   subsoil and the superjacent waters and with regard to other activities for
   the economic exploitation and exploration of the zone, such as the production
   of energy from the water, currents and winds
 * jurisdiction as provided for in international and domestic laws with regard
   to the establishment and use of artificial islands, installations, and
   structures, marine scientific research, and the protection and preservation
   of the marine environment
 * other rights and duties provided for under international and domestic laws

(See Presidential Proclamation No. 5030, March 10, 1983.)

Certain U.S. fisheries laws use the term “exclusive economic zone” (“EEZ”).
While its outer limit is the same as the EEZ on NOAA charts, the inner limit
generally extends landward to the seaward boundary of the coastal states of the
U.S. For the seaward limit of the states jurisdiction under the Submerged Lands
Act, please see GIS Data / Shapefiles.

Maritime Boundaries

Maritime boundaries with adjacent and opposite countries are established through
agreement and treaties with these neighboring nations.


ANNOUNCEMENTS

In 2011, the Office of Coast Survey completed a multi-year project to merge all
of the regional maritime limits into a single seamless digital dataset. Because
U.S. maritime limits change, based on accretion or erosion of the charted
shoreline, Coast Survey, in conjunction with the U.S. Baseline Committee,
continually maintains the dataset. When NOAA releases a new nautical chart the
maritime limits and boundaries are updated as needed. This page highlights
regional or local updates to the dataset.

September 13, 2013

Released version 4.1 with changes as follows:

 * updated 12nm and 24nm limits in the vicinity of Kuskokwim Bay, Alaska

July 22, 2013

Released version 4.0 with changes as follows:

 * updated 12nm, 24nm, and EEZ limits in several regions of Alaska
 * updated 12nm and 24nm limits in the Gulf of Mexico
 * updated 12nm, 24nm, and EEZ limits in the Atlantic Coast, near Massachusetts
 * updated 12nm, 24nm, and EEZ limits in the Pacific Northwest

July 20, 2012

Released version 3.1 with changes as follows:

 * updated 12nm, 24nm, and EEZ limits in several regions of Alaska

April 16, 2012

Released version 3.0 with changes as follows:

 * New links for downloadable data. NOAA has reformatted the dataset has been to
   better serve the user
 * updated 12nm, 24nm, and EEZ limits in Alaska
 * updated 12nm and 24nm limit lines in the Louisiana region of the Gulf of
   Mexico
 * updated limits in Puerto Rico following the release of a new chart


FREQUENTLY ASKED QUESTIONS

Where can I find electronic data of state territorial waters at 3 nautical miles
(or 9 nautical miles off of Texas, Puerto Rico, and the west coast of Florida)?

The Bureau of Ocean Energy Management (BOEM) manages and disseminates the
Submerged Lands Act federal/state boundaries. The data can be found under "GIS
Data / Shapefiles". The Gulf of Mexico dataset is available at "GOMR Geographic
Information System (GIS) Data and Maps".



How are the U.S. maritime limits drawn?

The U.S. maritime limits are projected from a "normal baseline" derived from
NOAA nautical charts. A "normal baseline" (as defined in the 1958 Geneva
Convention on the Territorial Sea and the Contiguous Zone and Article 5 of the
United Nations Convention of the Law of the Sea) is the low-water line along the
coast as marked on official, large-scale charts. Since "low-water line" does not
reference a specific tidal datum, the U.S. applies the term to reference the
lowest charted datum, which is mean lower low water (MLLW).

The maritime limits are created using "envelope of arcs," a method by which one
rolls a virtual circle along the charted low water line and selects salient
points. These salient points are called "contributing baseline points." Arcs
generated from these baseline points are blended together to form a continuous
limit line or envelope of arcs.



The U.S. Baseline Committee reviews and approves the limits of all maritime
zones on NOAA charts. It gains interagency consensus on the proper location of
the baseline, using the provisions of the 1958 Convention on the Territorial Sea
and the Contiguous Zone, to ensure that the seaward extents of U.S. maritime
zones do not exceed the breadth permitted by international law. Current members
of the Committee include the Departments of State (Chair), Commerce (NOAA),
Justice, Interior (BOEM), and Homeland Security (Coast Guard), among others.



What initiates updates to the digital U.S. maritime limits and boundaries?

The primary triggers for updates include accretion or erosion of the charted low
water line by approximately 500 meters or more, or changes to low tide
elevations (i.e., rocks awash) as a result of new hydrographic survey
information. The Office of Coast Survey and the Baseline Committee will
investigate these changes for new edition chart. There are approximately 12 new
editions issued each month, and a small number of these charts depict features
that impact the U.S. baseline or maritime limits. The Baseline Committee, which
meets four to six times per year, reviews and approved all proposed revisions.

Another trigger for change may be the U.S. ratification of a new treaty with a
neighboring coastal State. Some areas for future change include the U.S. waters
adjacent to Canada, the Bahamas, Kiribati, Tonga, and the Federated States of
Micronesia, to name a few.



How often are digital U.S. Maritime Limits and Boundaries updated?

Depending on the level of change (see Weekly Chart Updates), the Office of Coast
Survey may update the digital U.S. maritime limits and boundaries as often as
every few months in certain areas. Though we provide both dyanmic and static
datasets, we recommend using our dynamic data services to ensure the most
up-to-date version of the U.S. maritime limits and boundaries. We provide an
archive of past update annoucements (above) to explain what has changed in each
release of the data.



How do I use dynamic web mapping services?

We offer dynamic data is two formats: OpenGIS® Web Map Service (WMS) and
proprietary ESRI REST service.

The WMS can be used in various desktop GIS software as well as web mapping
applications. The link leads to the GetCapabilities page, which provides
easy-to-read, detailed information about the data as well as the necessary link
to load the data into a GIS or web mapping application. Open Geospatial
Consortium (OGC) provides more information about web mapping services.

For users who prefer to work within the ESRI software environment, we provide an
ESRI REST (Representational State Transfer) service. This service can be used in
ESRI’s ArcGIS Desktop software or in ESRI’s free ArcGIS Explorer Desktop. It can
also be added as a layer in web mapping services, such as ArcGIS Online.



What information is provided with the dataset?

The dataset includes specific information about each maritime boundary segment.
Attributes for the data are:

Boundary ID: a unique identifier of the boundary segment
Region Name: region in which the boundary is located
Type of Feature: features can either be a land boundary (between the U.S. and
Canada), a maritime limit, or a maritime boundary between the U.S. and an
adjacent or opposite country.
Publication Date: date the digital boundary was published online
Approval Date: date the U.S. Baseline Committee approved the updates
Legal Authority: treaty, agreement, or proclamation granting the government
authority to establish the limit or boundary
Agency of Responsibility: federal agency responsible for maintaining the digital
data
Note: additional notes about the limit/boundary
Supplemental Information Document: link to metadata about the specific boundary
segment. The document supplements the parent metadata record.
Unilateral Claim: some maritime boundary claims have not been agreed upon by all
parties. These boundaries are designated as unilateral claims.
Description: specific category of maritime limit/boundary.




Why is the digital product different from the product printed on the chart?

Because of a difference in the chart printing schedule and the digital data
update schedule, the digital data and the paper charts might not always be
identical. In the event that the digital product and the paper charts differ,
the maritime limits and boundaries on the paper charts take precedence.



We find that most people who seek this line are actually looking for the
Submerged Lands Act federal/state boundary provided by BOEM (see FAQ #1).

Related Links

Shore and Sea Boundaries

Maritime Limits White Paper

History of Maritime Zones under International Law

U.S. Maritime Boundary Treaties from Department of State

Maritime Zones and Boundaries - NOAA General Counsel



LAW OF THE SEA

HISTORY OF THE MARITIME ZONES UNDER INTERNATIONAL LAW
FROM THE CANNON SHOT RULE TO UNCLOS

For hundreds of years, the marine environment was free from regulation of
fishing, shipping, and resource exploitation. Over time, coastal States
(countries) had an increased interest in national security and the enforcement
of laws to protect its commerce and marine resources. As a result, a balance was
needed to maintain the freedom of navigation that many foreign maritime
interests had relied upon. This need for balance is captured in the history of
the law of the sea.

The birth of a nation’s authority to control its coastal waters has been traced
back to the sixteenth century. In the seventeenth century, the father of
international law and doctrine on the freedom of the seas, Grotius, recognized
the existence of a nation’s jurisdiction over the coastal waters that could be
effectively controlled from the land. The extent to which a nation could control
its coastal waters was largely based on the reach of its cannons on the shore.
Thus, the 3 nautical mile (nm) limit of the territorial sea resulted from what
is often referred to as the “cannon shot” rule. In the U.S., the creation of a
territorial sea and contiguous zone date back to as early as the late 1700s in
response to issues of national security and law enforcement at coastal areas,
including a 1793 diplomatic note sent from Thomas Jefferson and legislation
passed by Congress in 1799 to allow the boarding of foreign flag vessels within
12 nm from the coast. This zone was known as “customs waters” and was later
called the “Contiguous Zone.” By 1930 the proprietary rights of the coastal
state over the resources of the territorial sea was well established, provided
it did not interfere with a vessel’s right of innocent passage. In 1945,
President Truman issued a proclamation asserting rights to explore and exploit
the oil and gas resources of the continental shelf outside of the 3 nm
territorial sea. In 1953, the U.S. Congress enacted legislation over the federal
and state control of the continental shelf. In 1958, international conventions
were concluded in Geneva on the territorial sea, contiguous zone and continental
shelf. The concept of a fishery conservation zone was born in another Truman
Proclamation but Congress did not enact laws regarding a 200 nm fishery
conservation zone until 1976. This evolved into a zone whereby a coastal nation
had exclusive control over all economic exploration and exploitation of the
natural resources off its coast. By 1982, the custom of asserting a 12 nm
territorial sea, 24 nm contiguous zone, and 200 nm EEZ was codified in the
United Nations Convention on the Law of the Sea (UNCLOS).

U.S. CONTROL IN MARITIME ZONES VS RIGHTS OF FOREIGN STATES

The U.S. proclaimed a 12 nm territorial sea in 1988, a 24 nm contiguous zone in
1999, and a 200 nm EEZ in 1983, consistent with customary international law as
codified in UNCLOS. This customary law is a balanced compromise between a flag
State’s interest in maritime shipping and a coastal State’s interest in
protecting and managing its coastal waters. The U.S. sovereignty over its
terrestrial lands extends to its internal waters and territorial sea, including
the airspace above and the seabed below. Subject to ancient customs where
nations should provide safe harbor to ships in danger or distress (force
majure), the U.S. may restrict entry or travel through its internal waters. The
U.S. may also prohibit the entry into portions of the territorial sea, provided
there is still an area that allows for vessels to exercise their right of
innocent passage through the territorial sea. “Passage” through the territorial
sea must be continuous and expeditious, although that may include stopping and
anchoring under certain circumstances. While warships are generally immune from
laws and regulations, the U.S. has the right to require foreign warships comply
with U.S. laws. If they don’t, the U.S. may order the foreign warship to leave
its territorial sea.

The contiguous zone is a buffer to the territorial sea, and within it, the U.S.
may exercise the control necessary to prevent infringement of its customs,
fiscal, immigration or sanitary laws and regulation of territorial sea. In
addition, the U.S. may regulate the removal of cultural heritage, including
foreign flagged vessels and nationals in its contiguous zone. It overlaps the
EEZ which extends from the territorial sea out to 200 nm. The U.S. does not
exercise sovereignty in the contiguous zone or the EEZ. It does have exclusive
sovereign rights and jurisdicton for exploration and exploitation of natural
resources of the seabed, subsoil, water column, and air space in the EEZ.

All of these zones have a common point of reference from which they are
measured: the baseline. The rules for determining the baseline under UNCLOS are
substantively the same as those under the 1958 Convention, which the U.S.
ratified in 1961. As a line that marks the inner limit of the territorial sea
and the outer limit of internal waters, the baseline is comprised of the low
water line on NOAA charts plus closing lines across legally-defined bays and
rivers. The U.S. uses a normal baseline, as opposed to a straight baseline
because of its interests in preserving the freedom of navigation. One of the
most important facts for those relying on NOAA’s charts for the limits of these
zones is that the baseline and all of the zones are ambulatory. They are subject
to change due to accretion and erosion of the shore.

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