Skip to content

Border Security Along the Southwest Border: Fact Sheet


*This is an updated version of a March 2019 fact sheet on the same topic*

How secure is the Southwest Border?

America’s Southwest border has never been more secure.

The U.S. has built more physical barriers, is using more advanced surveillance technology, has stationed more agents, and has allocated more funds to the border than ever before.

Following the passage of the Secure Fence Act in 2006, the Bush and Obama administrations constructed nearly 700 miles of reinforced physical barriers along the 2,000-mile Southwest border. At significant cost, the Trump administration constructed 455 miles of additional physical barriers along the Southwest border, although much of the new construction replaced smaller fencing or vehicle barriers with 30-foot steel and concrete bollards. The focus on replacing existing barriers was due to the existence of rugged terrain and the Rio Grande already serving as natural barriers along many other parts of the border.

In addition to barriers, U.S. Customs and Border Protection (CBP) also relies heavily on technology to secure the Southwest border. Using technology typically costs less than constructing physical barriers, is less intrusive, and serves as a better force multiplier. CBP utilizes a host of border security technologies, including fixed towers, mobile surveillance systems, remote video surveillance systems, thermal imaging systems, radiation portal monitors, ground sensors, license plate readers, and unmanned aerial surveillance including Predator B drones.

To complement physical barriers and advanced technology, the U.S. Border Patrol stationed 16,731 agents at the Southwest border in Fiscal Year (FY) 2019, the last year for which data is available. This marks a significant increase in manpower over recent decades, representing nearly double the number of border agents stationed at the border in FY 2000, and more than triple the number stationed in FY 1995. As of April 2019, CBP is also staffing approximately 24,392 agents at various ports of entry (land ports of entry at the Southwest border, as well as sea ports and airports).

In addition, between FY 2000 and FY 2020, Congress increased the Border Patrol’s budget approximately 445%, from about $1.1 billion to about $4.9 billion. The Trump administration also allocated over $13 billion to border wall construction from FY 2017 to FY 2021, including by using emergency authority to re-direct Department of Defense (DOD) funds from military pay, pensions, and construction projects. Since FY 2017, Congress has also allocated more than $700 million in funding specifically for an array of new tools and technologies designed to increase surveillance capabilities along the border.

Border Patrol Agents Stationed at the Southwest Border (FY 1995-FY 2019)

Is the overall number of apprehensions at the Southwest border a good metric for measuring the security of the border?

No, overall apprehension statistics do not correlate well with border security or effectiveness.

Total encounter or apprehension numbers are a flawed metric for measuring border security, representing the number of people seeking to enter the United States (and getting caught) as opposed to providing a true measure of the safety or effectiveness of border security. Notably, apprehension statistics tend to increase as border security increases, with the investments in border personnel and infrastructure in recent decades leading to a larger proportion of those seeking entry being apprehended. In addition, apprehension numbers do not even adequately represent the overall number of arriving migrants. They do not measure those who evade detection (colloquially known as “got aways,” a group for which CBP does not track reliable data), and particularly in recent months, they have also been inflated by many migrants who are summarily turned back due to pandemic-related health rules and make multiple unsuccessful attempts to cross repeatedly within a short time span.

Border Patrol’s primary mission at the border is to “prevent terrorists and terrorist weapons from entering the United States, and to detect, interdict, and apprehend those who attempt to enter illegally or smuggle any person or contraband across the nation’s borders.” The total number of overall apprehensions at the Southwest border does not provide clear information about any of these priorities.

Do migrants crossing the U.S.-Mexico border pose a terrorist or national security threat to the U.S.?

No, the supposed national security threats posed by migrants entering at the Southwest border is not borne out by facts.

According to a Cato Institute report, zero people have ever died or been injured from terrorist attacks on U.S. soil committed by an individual who crossed the Southwest border without authorization. As a group, immigrants are less likely to commit violent and property crimes when compared to native-born U.S. citizens. Undocumented immigrants in particular have a considerably lower felony rate than both legal immigrants and native-born U.S. citizens. Based on the data, increases in migration at the Southwest border are far more likely to pose humanitarian concerns than security ones.

Some reports and politicians have noted that occasionally those on security-based watch lists are apprehended by CBP at the border, but it is important to be precise about how many such interdictions occur and what threat, if any, presence on each list might signify.

Broadly, there are two separate lists CBP checks against to determine whether an individual may pose a potential national security or terrorism risk upon apprehension at the border. The first is the FBI’s terrorist watchlist, which mainly includes identifying information relating to individuals in the Known or Suspected Terrorist (KST) file. KSTs are individuals who have either been charged, arrested, or convicted of a crime related to terrorism or those who are reasonably suspected to be engaging in or intending to engage in terrorist activities. The watchlist is a very broad master list including anyone suspected of terrorism-related activities, and it includes smaller sub-lists for individuals that pose a higher risk (such as the No Fly List, which consists of approximately 7% of the names on the master watchlist). As of 2017, the terrorism watchlist had 1.16 million names on it, although some individuals are only identified by surnames and limited biographical details. Only a small number of the names on the list are likely to be actual terrorists, and only a tiny fraction (.08%) of KSTs apprehended attempting to enter the U.S. are encountered at the Southwest border.

Attempts of entry by individuals that are known or suspected terrorists or associates of terrorists are extremely rare on the Southwest border. According to a September 2020 whistleblower complaint, no more than three KSTs were apprehended at the border in Fiscal Year 2017. CBP and other agencies had encountered 3,752 KSTs at airports and in the interior in the same time period. In March 2021, CBP told Congress that it had apprehended four individuals on the terrorist watchlist at the border in the preceding 6 months.

Known and Suspected Terrorist Apprehensions (FY 2017)

 The second list is based on a CBP term of art called Special Interest Aliens (SIAs). SIAs are individuals who have traveled through or are coming from any of a list of 30-50 countries identified as having a possible link to terrorism. The current list of designated countries is not publicly available, but in years past it has included several countries in the Americas, including Argentina, Brazil, and Panama. There are no additional criteria for being considered an SIA other than presence in one of these countries prior to arrival at the border. DHS has reported that over 3,000 SIAs are apprehended at the border each year.

DHS has made clear that SIA and KST apprehensions should not be conflated, and that most KSTs are apprehended at airports rather than the border.

Do additional enforcement measures deter arriving unauthorized migrants?

Most available evidence suggests stricter enforcement does not deter irregular migration.

Since at least 1994, various administrations have attempted to increase enforcement measures and impose harsher conditions on arriving migrants as a means to reduce the total number of individuals attempting to cross the Southwest border between ports of entry. The 1994 Prevention Through Deterrence (PTD) strategy aimed to push arriving migrants away from border cities and into rough and dangerous terrain to ultimately deter future attempts to cross. In 2005, Operation Streamline emphasized the prosecution and detention of arriving migrants, in part as an attempt to deter future migration. Presidents Obama and Trump both touted their efforts at barrier construction on the Southwest border — among other enforcement measures — as a means of deterring unauthorized migrants.

However, none of these approaches proved to be effective at deterring irregular migration. The Clinton administration’s PTD strategy led to CBP apprehensions of unauthorized migrants spiking in the early 2000s. And while Operation Streamline was implemented during a long-term decline in unauthorized migration, a statistical analysis of the program’s impact found no deterrent effect. Obama and Trump both presided over large increases in irregular migration in 2014, 2016, and 2019.

While enforcement is not correlated with deterrence, effective and targeted enforcement measures at the Southwest border can result in more orderly, secure, and humane processing of those who do arrive and attempt to cross.

Would constructing additional barriers on the Southwest border be a good use of resources?

In most circumstances, building additional barriers is not cost effective, although barrier maintenance and gap filling remains essential in specific locations along the border.

Constructing a 2,000 mile wall — as the Trump administration initially intended — would be an expensive endeavor without being particularly effective. The cost of building a wall along the entire Southwest border has been estimated to range from $21.6 billion to $31.2 billion, not including the cost of maintaining the wall and other physical barriers over the years. The Trump administration already spent more than $10 billion on barriers over the past four years, constructing on top of 654 miles of border fencing that had been constructed from 2006 to 2015.

However, certain locations at the border are in need of additional barrier construction. President Biden issued an executive order on January 20 which immediately paused all construction of barriers along the border. After the pause, there have been reports of notable gaps in certain locations, as well as areas needing new maintenance or construction for reasons related to the structural integrity of certain parts of border walling. In cases such as these, continued construction of robust barriers would be a good use of resources.

According to an April 5 report, the Biden administration is planning to restart construction to plug some of the gaps along the border.

Are there obvious investments in border security resources that would be effective?

Yes, investments in ports of entry are needed and would be an effective use of funds. 

Congress should invest in the CBP Office of Field Operations (OFO), which oversees the flow of commerce and immigrants at all 328 ports of entry in the nation. CBP OFO currently has a staffing shortage of at least 2,700 port of entry officers, representing a border security vulnerability. CBP also found in 2014 that adding a single CBP OFO officer to a port of entry would result in annual benefits of a $2 million increase in our country’s Gross Domestic Product (GDP), $640,000 saved in opportunity costs, and 33 jobs added to the economy, because it would help speed the flow of commerce.

What is the best way to reduce drug smuggling along the Southwest border?

Through focusing on investments at ports of entry.

CBP statistics show that in the first six months of FY 2021, CBP OFO officers seized 131,086 pounds of cocaine, heroin, methamphetamine and fentanyl at ports of entry, compared to 19,587 pounds seized by the Border Patrol between ports of entry. The data demonstrates in recent months, 87% of hard drugs were seized at ports of entry, a trend that has remained consistent for years.

Congress must invest in infrastructure and staffing at ports of entry to help curtail drug trafficking. Investments in border security between ports of entry, including investments in physical barriers and more Border Patrol agents, are not effective means of preventing dangerous drugs from entering American communities.

What other policies are effective in promoting border security?

Carrizo cane/salt cedar plant eradication, improved interagency coordination, and immigration reform all would promote stronger border security.

A new program to eradicate invasive plants that block the view of Border Patrol agents would be a cheap and effective way to improve border security. A federal program to eradicate the invasive and non-native carrizo cane and salt cedar plants along the Rio Grande Valley in Texas would provide the Border Patrol with greater visibility agents and access to the Rio Grande.

In addition, promoting additional interagency coordination at the border would allow CBP and Border Patrol to focus on their mission of intercepting unauthorized crossers and promoting orderly, secure, and efficient trade and movement across the border. This coordination might include co-locating Office of Refugee Resettlement staff, Federal Emergency Management Association (FEMA) personnel, case management workers, mental health professionals, and others in Border Patrol stations, which would provide for smoother processing of migrants. For example, improving interagency coordination through co-locating key agencies would relieve CBP agents from needing to spend time processing unaccompanied children and other asylum seekers — a critical task but one for which they do not have significant training or expertise.

Finally, leading national security officials agree that broad reforms to our immigration system will bolster national security and maintain U.S. global interests. A updated immigration system that promotes safety and security, benefits American workers and our economy, and provides earned legalization for otherwise law-abiding undocumented immigrants living in the U.S. would promote security at our borders. Reforming the current system could ensure that future labor needs are fulfilled by our legal immigration system, reducing the need for migrants to cross the Southwest border without authorization and allowing CBP and other law enforcement agencies to focus on apprehending individuals who pose threats to public safety.

Learn More

Read more about Experts Discuss Solutions to Address the Situation at the Southern Border


Experts Discuss Solutions to Address the Situation at the Southern Border

Read more about What's Happening at the Southern Border, Explained

Fact Sheet

What's Happening at the Southern Border, Explained

Read more about Bill Analysis: The Bipartisan Border Solutions Act

Bill Summary

Bill Analysis: The Bipartisan Border Solutions Act