The United States has never permanently closed its borders, but it has imposed sweeping entry restrictions several times. The clearest modern example of when the US closed its borders came on March 21, 2020, when land crossings with Canada and Mexico were shut to nonessential travel for roughly 19 months during the COVID-19 pandemic. Before that, the most dramatic closure was the complete shutdown of US airspace on September 11, 2001. Earlier restrictions during World War I and the 1918 flu pandemic tightened who could cross, and more recent presidential proclamations in 2024 and 2025 sharply restricted asylum at the southern border without formally sealing the ports.
The COVID-19 Land Border Closure, March 2020 to November 2021
At 11:59 p.m. EDT on March 20, 2020, the Department of Homeland Security imposed temporary restrictions on all nonessential travel at US land ports of entry and ferry crossings with both Canada and Mexico.1Federal Register. Notification of Temporary Travel Restrictions Applicable to Land Ports of Entry and Ferries Service The legal authority came from 19 U.S.C. § 1318, which allows the government to close ports of entry or take lesser measures in response to a “specific threat to human life or national interests.”2GovInfo. Extension of Temporary Travel Restrictions at Land Ports of Entry
The closure was not absolute. Commercial trucking, medical personnel, military members, and US citizens and lawful permanent residents returning home continued to move across. What stopped was casual crossing: shopping, tourism, family visits, and other routine trips. More than 230,000 people had been using those ports daily before the shutdown, and pedestrian and passenger crossings at Texas ports fell 62 percent in the first eight months.3Baker Institute. Mexican Consumption and Economic Impact of Coronavirus on Texas Border Counties
Both governments renewed the restrictions month after month.4Baker Institute. Reopening the US-Mexico Border: A Framework for Action5CBC. US Land Border Reopens to Vaccinated Travelers6BBC. US-Canada Border Reopens After 19 Months
Title 42, March 2020 to May 2023
Running alongside and outlasting the land closure was a separate public health order. On March 20, 2020, the Centers for Disease Control and Prevention issued a Title 42 order authorizing the rapid expulsion of migrants, including asylum seekers, without normal immigration processing.7Congressional Research Service. Title 42 Public Health Order and Immigration
The Biden administration tried to end the order in April 2022, setting a termination date of May 23, 2022, but a federal district court blocked the move with a nationwide preliminary injunction.7Congressional Research Service. Title 42 Public Health Order and Immigration8Migration Policy Institute. Title 42 Autopsy9Doctors Without Borders. What the End of Title 42 Means for People Seeking Safety at the US Border
The September 11, 2001 Airspace Shutdown
The most dramatic short closure in modern US history was not at the land border but in the sky. At 9:40 a.m. on September 11, 2001, the FAA ordered every aircraft in the national airspace to land. By 9:45 a.m., US airspace was completely shut, with only military aircraft and Air Force One permitted to fly. It was the first complete shutdown of the national airspace in history.10FAA. FAA Response to the 9/11 Attacks11AOPA. GA Remembers 9/11
Commercial airports began reopening two days later, on September 13. International general aviation flights to and from Canada and Mexico were not permitted again until November 8, 2001.11AOPA. GA Remembers 9/11 Land ports of entry were not formally sealed, but screening at every border changed. Security procedures were standardized and intensified, biometric identification was introduced, and face-to-face visa interviews became mandatory for nearly all applicants by May 2003. Arrivals from countries outside the Visa Waiver Program had not returned to pre-2001 levels by 2007.12DHS. 9/11 and Travel to the US
World War I and the 1918 Flu
The border has been tightened before without being closed. During World War I, President Woodrow Wilson issued Executive Order 2932 on August 8, 1918, creating a comprehensive permit-and-passport system for anyone entering or leaving the country. Control officers could deny passage to anyone whose movement they deemed “prejudicial to the interests of the United States,” and applicants had to submit sworn applications with photographs weeks in advance.13U.S. Department of State. Executive Order 2932
The 1918 influenza pandemic, by contrast, did not produce a national border closure. Immigration stations stayed open and adapted to isolate and treat sick arrivals rather than turn them away.14USCIS. The 1918 Influenza Epidemic and the Bureaus of Immigration and Naturalization Localized controls were another story. Alaska’s territorial governor imposed quarantine on all incoming ships starting October 15, 1918, and several remote Alaskan communities set up armed checkpoints that kept the virus out entirely.15CDC. Nonpharmaceutical Interventions During the 1918-1920 Influenza Pandemic
The 2024 and 2025 Asylum Restrictions
Recent restrictions at the southern border have targeted asylum rather than shutting the ports themselves. On June 5, 2024, President Biden issued a proclamation under Section 212(f) of the Immigration and Nationality Act directing DHS to restrict asylum processing when the seven-day average of daily border encounters exceeded 2,500. The restrictions would lift only after that average dropped below 1,500 for seven consecutive days, plus a two-week lag. Biden’s order kept asylum processing open at official ports through the CBP One app and exempted unaccompanied children and trafficking victims.16BBC. Biden Issues Executive Order to Restrict Asylum at US-Mexico Border17Federal Register. Securing the Border Interim Final Rule
On January 20, 2025, President Trump issued Proclamation 10888, “Guaranteeing the States Protection Against Invasion,” invoking Sections 212(f) and 215(a) of the INA to suspend the entry of individuals the administration described as part of an “invasion” at the southern border. The proclamation also barred those individuals from invoking asylum protections and remains in effect until the president determines the “invasion” has ended.18Congressional Research Service. Proclamation Guaranteeing the States Protection Against Invasion19AILA. President Trump Signs Executive Order Guaranteeing the States Protection Against Invasion A companion executive order, “Securing Our Borders,” ended the CBP One app, restarted the Migrant Protection Protocols, and terminated categorical parole programs for Cubans, Haitians, Nicaraguans, and Venezuelans. Refugee admissions were separately suspended for at least 90 days beginning January 27, 2025.20White House. Securing Our Borders
The effect on the ground was steep. Between February and September 2025, Border Patrol processed more than 94 percent of encountered migrants for expedited removal, voluntary return, or ICE detention. Southwest border encounters fell from 2.1 million in fiscal year 2024 to roughly 444,000 in fiscal year 2025, the lowest apprehension levels since 1966.21Migration Policy Institute. A New Era of Enforcement Under Trump22WOLA. US-Mexico Border Update
On April 24, 2026, the US Court of Appeals for the D.C. Circuit ruled in RAICES v. Mullin that Proclamation 10888 was unlawful insofar as it displaced the INA’s removal framework with extra-statutory procedures blocking noncitizens from seeking asylum and other protection.23U.S. Court of Appeals for the D.C. Circuit. RAICES v. Mullin, No. 25-524324ACLU. Federal Appeals Court Rules Trump Proclamation Eliminating Asylum Is Unlawful Two months later, on June 25, 2026, the Supreme Court held 6-3 in Mullin v. Al Otro Lado that a person standing in Mexico who tries but fails to enter does not “arrive in” the United States for INA purposes and cannot claim asylum under the statute. Justices Sotomayor, Kagan, and Jackson dissented.25Supreme Court of the United States. Mullin v. Al Otro Lado, No. 25-5
What Authority the President Actually Has
Whether a president can truly “close the border” depends on which border and which travelers. Section 212(f) of the INA lets the president suspend the entry of “all aliens or any class of aliens” whose entry would be “detrimental to the interests of the United States.” The Supreme Court upheld the breadth of that authority in Trump v. Hawaii (2018), holding that the statute “exudes deference to the President” on national security. Separately, 19 U.S.C. § 1318(b)(2) lets the Commissioner of Customs and Border Protection temporarily close any port of entry in response to a specific threat to human life or national interests.26TRAC Reports. Can the President Close the Border
There are hard limits. US citizens have a substantive right to enter the country, and lawful permanent residents cannot be denied entry without a fair hearing. The INA also guarantees that any person who “arrives in the United States” may apply for asylum. The D.C. Circuit’s 2026 ruling in RAICES v. Mullin reinforced that the president’s power to suspend entry does not authorize the executive branch to dismantle the congressionally created framework for people already on US soil.23U.S. Court of Appeals for the D.C. Circuit. RAICES v. Mullin, No. 25-5243 Put simply, the country can restrict who arrives, tighten how they are screened, and even shut its ports to routine traffic during an emergency. What it has not done, and legally cannot do by executive action alone, is close itself off from the people the law already protects.