According to the U.S. Geological Survey (USGS), the length of the International Boundary line of the U.S.-Canadian border, excluding Alaska, is approximately 3,987 miles, while the length of the U.S.-Mexican border is estimated at 1,933 miles. The length of the Alaska-Canada border alone is 1,538 miles. The tables below list the 13 U.S. states that share international boundaries with Canada and the four states that share an international border with Mexico, with information from the International Boundary Commission and the U.S. Geological Survey. The National Oceanic and Atmospheric Administration (NOAA) has surveyed the coastline of the continental United States, Alaska, and Hawaii several times. The current figures for the coastline are the results of the measurements done originally in 1915 and updated several times thereafter. These figures reflect the general outline of the seacoast. The figures for Alaska reflect a 1961 remeasurement. It is important to note that boundary and coastline distances can differ significantly based on the scale used on the maps or charts. The Canadian and Mexican international borders are less problematic than the coastline measures because there are long stretches that are straight, such as the nearly 900-mile section of the U.S.-Canadian border along the 49 th parallel. Coastline measurements are more difficult because of the effects of tides and the necessarily arbitrary decisions that must be made about measuring bays, coves, islands, and inlets leading to streams and rivers. The "general coastline" data in this report are based on large scale nautical charts, resulting in a coastline measure for the 50 states totaling12,383 miles. Another measure using smaller scale nautical charts more than doubles this measurement to 29,093 miles, while the figures used by the NOAA in administering the Coastal Zone Management program (16 U.S.C. §1451) come to 88,612 miles (not including the Great Lakes). Table 3 provides figures for the areas of the U.S. coastline bordering international waters. It measures the coastline of the contiguous states from northeast to northwest. Similar to problems mentioned above regarding measuring coastlines, variations in shoreline figures appear due to natural occurrences, including bays and inlets, and in differing methods of measurement. These shoreline lengths were measured in 1970 by the International Coordinating Committee on the Great Lakes Basic Hydraulic and Hydrologic Data. CRS Report RS22026, Border Security: The San Diego Fence , by [author name scrubbed] and [author name scrubbed]. CRS Report RL33659, Border Security: Barriers Along the U.S. International Border , by [author name scrubbed] and Yule Kim.CRS Report RL33353, Civilian Patrols Along the Border: Legal and Policy Issues , by [author name scrubbed] and [author name scrubbed]. CRS Report RS22443, Border Security and Military Support: Legal Authorizations and Restrictions , by [author name scrubbed]. CRS Report RL33106, Border Security and the Southwest Border: Background, Legislation, and Issues , by Lisa M. Seghetti et al.. CRS Report RL31826, Protecting the U.S. Perimeter: " Border Searches " Under the Fourth Amendment , by Yule Kim. CRS Report RL32399, Border Security: Inspections Practices, Policies, and Issues , by [author name scrubbed] et al., Border Security: Inspections Practices, Policies, and Issues, coordinated by [author name scrubbed]. Shalowitz, Aaron L. Shore and Sea Boundaries , vol. 2. Washington: U.S. Dept. of Commerce, Coast and Geodetic Survey, 1964. Coast and Geodetic Survey Publication 10-1. U.S. Census Bureau. Statistical Abstract of the United States 2007. Washington: GPO, 2006. U.S. Department of Commerce, National Oceanic and Atmospheric Administration. The Coastline of the United States , 1975. Van Zandt, Franklin K. Boundaries of the United States and the Several States . Washington: GPO, 1976. Geological Survey Professional Paper 909. The World Almanac and Book of Facts 2007. International Boundary and Water Commission (IBWC) United States and Mexico http://www.ibwc.state.gov This website has historical information on the two treaties—the Guadalupe Hidalgo Treaty of February 2,1848, and the Treaty of December 30, 1853—between the United States and Mexico that set the international boundary between the two countries. Also included is information on additional conventions and treaties between the two nations on maintaining the Rio Grande and Colorado Rivers, as well as current IBWC reports and solutions for boundary and water problems. International Boundary Commission between Canada and the United States http://www.internationalboundarycommission.org This website contains information on the Treaty of 1908 between the United States and Canada that completed the mapping of the international boundary from the Atlantic Ocean to the Pacific Ocean. Information on U.S.-Canadian border history and boundary markings along open vistas is also included.

Summary: This report, originally authored by CRS Information Specialist Barbara Torreon, provides information on the international boundaries that the United States shares with Canada and Mexico. Included are data on land and water boundaries for the northern Canadian border and the southern Mexican border, as well as the international boundaries for the U.S. states that border these countries. Coastline figures for the continental United States, Alaska, Hawaii, the Great Lakes, and extraterritorial areas are also included. This report does not cover border security issues; however, a listing of relevant CRS reports is at the end of this report. This report will be updated as needed.