U.S. Maritime Limits & Boundaries

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.

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

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).