Federal and Indian Lands on the U.S.-Mexico Border
February 21, 2018
Federal and Indian Lands on the U.S.-Mexico Border
The federal government owns roughly 640 million acres of
is the breadth of agencies reflected, specifically whether all
land, about 28% of the 2.27 billion acres of land in the
or a subset of federal lands are captured. Similarly, some
United States. In addition, the Bureau of Indian Affairs
estimates might include Indian lands with the estimate of
(BIA), in the Department of the Interior (DOI), is
federal lands. Another factor is the source(s) used. Major
responsible for administering another 55 million acres held
geographic information system (GIS) sources of federal and
in trust for American Indians, Indian tribes, and Alaska
Indian lands include the National Atlas, Protected Areas
Natives. Congress faces diverse issues pertaining to the
Database of the United States (PAD-US), and the U.S.
management, development, and protection of federal and
Census (for Indian lands only). These sources reflect land
Indian lands.
ownership as of differing dates, and they vary in terms of
precision and scale, among other variables. In addition,
Federal and Indian lands on the border between the United
there are differing sources of GIS data from which the
States and Mexico present unique challenges due to the
international border can be derived, and these sources can
remoteness and topography of the lands, length of the
result in varying calculations of border length.
border, extent of federal and Indian lands, and differences
in missions of managing agencies. These challenges are
It is sometimes unclear from GIS sources whether federal
particularly at issue during congressional consideration of
or Indian lands are on the border or are located instead in
proposals to secure the nation’s borders against terrorists
close proximity to the border. In these cases, differing
and illegal entry of persons and goods, including through
judgments could be made as to the inclusion of these areas.
construction of fences and other barriers. Questions include
Further, some estimates may seek to capture only lands on
how to facilitate access to these lands that allows for efforts
the border whereas others might also seek to reflect lands in
to enhance border security while at the same time
close proximity (e.g., within one mile of the border).
protecting natural and cultural resources and addressing
environmental damage related to illegal cross-border
Variation in border mileage estimates also occurs based on
activities.
the extent to which water features on the border are
reflected in addition to land areas. Along the U.S.-Mexico
This CRS In Focus provides an estimate of total linear
border, federal areas that contain sizeable areas of water
miles of federal and Indian land on the southwestern border.
include two areas in Texas: Amistad National Recreation
It also identifies the portions of these lands managed by
Area (National Park Service, or NPS), consisting of the
each federal agency in each of the four states along the
U.S. portion of the International Amistad Reservoir, and the
border—Arizona, California, New Mexico, and Texas.
Lower Rio Grande Valley National Wildlife Refuge (Fish
and Wildlife Service), located at the southern tip of Texas
For an overview of federal land ownership, see CRS Report
where the Rio Grande flows into the Gulf of Mexico.
R42346, Federal Land Ownership: Overview and Data, by
Carol Hardy Vincent, Laura A. Hanson, and Carla N.
CRS Estimate
Argueta. For an overview of natural resource policy and
management issues related to federal lands, see CRS Report
Mileage
R43429, Federal Lands and Related Resources: Overview
CRS estimates 693 miles of both federal and Indian land on
and Selected Issues for the 115th Congress, coordinated by
the border, representing approximately 35% of the 1,965
Katie Hoover.
miles on the southern international border. These lands are
Differing Estimates
administered by a total of seven agencies.
There is no single, authoritative estimate of linear miles of
Six of the seven agencies manage federal lands. They are
federal and Indian lands on the U.S. border with Mexico.
the NPS, Bureau of Land Management (BLM), Fish and
Instead, widely differing estimates have been reported in
Wildlife Service (FWS), and Bureau of Reclamation
recent years, depending on the objectives established,
(BOR), all in DOI; the Forest Service, in the Department of
sources consulted, and approaches used. Past estimates
Agriculture; and the Department of Defense. The seventh
have included 632 miles (Government Accountability
agency, BIA, is the primary federal agency charged with
Office, or GAO), 648 miles (U.S. Geological Survey, or
carrying out the U.S. trust responsibility to American
USGS), and 820 miles (DOI). For some of these estimates,
Indians, as noted, and thus Indian lands are reflected herein
there is insufficient information publicly available to
under “BIA.”
determine how they were prepared and why they differ.
These seven agencies manage differing amounts of land on
A variety of factors can affect federal land estimates and
the border, ranging from 10.1 miles for BOR to 195.1 miles
likely account for much of the variation in reported
for NPS. Of the four states, the most federally managed
estimates of federal and Indian border mileage. One factor
border mileage is in Arizona (298.5 miles) and the least is
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Federal and Indian Lands on the U.S.-Mexico Border
in California (61.0 miles). Table 1 contains the number of
Indian Affairs; FS = Forest Service; DOD = Department of Defense;
federal and Indian border miles by agency and state. Figure
BOR = Bureau of Reclamation. Both agencies and states are listed in
1 portrays all federal and Indian lands on the border, and
descending order of mileage of federal and Indian lands.
Figure 2 depicts these border lands by agency.
Sources and Methodology
Table 1. Federal and Indian Lands on the
The CRS estimate of 693 miles of federal and Indian lands
U.S. Border with Mexico
on the border reflects lands managed by any federal agency
(by agency and state, in linear miles)
as well as Indian trust lands under BIA. PAD-US was the
primary source, because of the currency of the information
Agency
AZ
TX
NM
CA
Total
(2016) and the detail as to ownership of small land parcels.
U.S. Census Bureau data also were used for Indian lands
NPS
37.8
157.3
0
0
195.1
and to identify the international border; these data reflect a
(28.1%)
total U.S.-Mexico border length of approximately 1,965
BLM
30.7
0
81.7
60.4
172.8
miles, as noted above. Further, to compare sources and
(24.9%)
methodology, CRS consulted with agency staff, including
staff of the USGS and GAO who specialize in GIS data and
FWS
63.0
94.2
0
0.6
157.8
take a lead role in federal government estimates of federal
(22.8)%
and Indian border lands.
BIA
71.2
0.7
0
0
71.9
The 693 miles is an estimate of federal and Indian lands
(10.4%)
with a boundary on the border as opposed to lands within a
FS
48.5
0
0
0
48.5
certain distance of the border. In some cases, it was difficult
(7.0%)
to determine whether federal or Indian lands shared a
boundary with the border or were instead in very close
DOD
37.2
0
0
0
37.2
proximity. CRS made these determinations based on a
(5.4%)
visual analysis of the GIS data, and other analysts could
BOR
10.1
0
0
0
10.1
make different judgments.
(1.5%)
With regard to water features, the estimate of 693 miles
Total
298.5
252.2
81.7
61.0
693.4
includes 94.2 miles within the Lower Rio Grande Valley
(43.0%) (36.4%) (11.8%) (8.8%)
(100.0%)
National Wildlife Refuge and 36.4 miles of the Amistad
Source: CRS, using data from the Protected Areas Database of the
National Recreation Area. However, the estimate does not
United States at https://gapanalysis.usgs.gov/padus/data/, August 2016,
include another 47.5 miles in Amistad consisting of waters
and U.S. Census Bureau, TIGER/Line Shapefiles at
that follow the international boundary (mid-channel in the
https://www.census.gov/cgi-bin/geo/shapefiles/index.php.
Rio Grande), where there is no apparent adjacent dry land
owned by the federal government.
Notes: NPS = National Park Service; BLM=Bureau of Land
Management; FWS = Fish and Wildlife Service; BIA = Bureau of
Figure 1. Federal and Indian Border Lands
Figure 2. Federal and Indian Border Lands by Agency
Sources (Figure 1 and Figure 2): CRS, using data from the Protected Areas Database of the United States, U.S. Census Bureau, and Esri
2016 Data and Maps.
James C. Uzel, Geospatial Information Systems Analyst
IF10832
Carol Hardy Vincent, Specialist in Natural Resources
Policy
https://crsreports.congress.gov
Federal and Indian Lands on the U.S.-Mexico Border
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