Illegal immigration to the United States in the context of "Mexico–United States border"

Throughout U.S. history, the country experienced successive waves of immigration, particularly from Europe and later on from Asia and from Latin America. Colonial-era immigrants often repaid the cost of transoceanic transportation by becoming indentured servants where the employer paid the ship's captain. In the late 19th century, immigration from China and Japan was restricted. In the 1920s, restrictive immigration quotas were imposed but political refugees had special status. Numerical restrictions ended in 1965. In recent years, the largest numbers of immigrants to the United States have come from Asia and Central America (see Central American crisis).

Attitudes towards new immigrants have fluctuated from favorable to hostile since the 1790s. Recent debates have focused on the southern border (see Illegal immigration to the United States and Mexico–United States border wall) and the status of "dreamers", people who illegally migrated with their families when they were children and have lived in the U.S. for almost their entire lives (see Deferred Action for Childhood Arrivals).

A border wall has been built along portions of the Mexico–United States border in an attempt to reduce illegal immigration to the United States from Mexico. The barrier is not a continuous structure but a series of obstructions variously classified as "fences" or "walls".

Between the physical barriers, security is provided by a "virtual fence" of sensors, cameras, and other surveillance equipment used to dispatch United States Border Patrol agents to suspected migrant crossings. In May 2011, the Department of Homeland Security (DHS) said it had 649 miles (1,044 km) of barriers in place. A total of 438 miles (705 km) of new primary barriers were built during Donald Trump's first presidency, dubbed the "Trump wall", though Trump had repeatedly promised a "giant wall" spanning the entire border and that Mexico would "pay for the wall," neither of which were done. The national border's length is 1,954 miles (3,145 km), of which 1,255 miles (2,020 km) is the Rio Grande and 699 miles (1,125 km) is on land.

Ronald Reagan's tenure as the 40th president of the United States began with his first inauguration on January 20, 1981, and ended on January 20, 1989. Reagan, a Republican from California, took office after defeating the Democratic incumbent president Jimmy Carter and independent congressman John B. Anderson in the 1980 presidential election. Four years later, he won re-election in the 1984 presidential election, after defeating the Democratic nominee Walter Mondale. Bush was constitutionally limited to two terms and was succeeded by his vice president, George H. W. Bush, who won the 1988 presidential election. Reagan's 1980 landslide election resulted from a conservative shift to the right in American politics, including a loss of confidence in liberal, New Deal, and Great Society programs and priorities that had dominated the national agenda since the 1930s.

Domestically, the Reagan administration enacted a major tax cut, sought to cut non-military spending, and eliminated federal regulations. The administration's economic policies, known as "Reaganomics", were inspired by supply-side economics. The combination of tax cuts and an increase in defense spending led to budget deficits, and the federal debt increased significantly during Reagan's tenure. Reagan signed the Tax Reform Act of 1986, simplifying the tax code by reducing rates and removing several tax breaks, and the Immigration Reform and Control Act of 1986, which enacted sweeping changes to U.S. immigration law and granted amnesty to three million illegal immigrants. Reagan also appointed more federal judges than any other president, including four Supreme Court Justices.

Mohammed Mani Ahmad al-Qahtani (Arabic: محمد ماني احمد القحطاني; sometimes transliterated as al-Kahtani; born November 19, 1975) is a Saudi citizen who was detained as an al-Qaeda operative for 20 years in the United States's Guantanamo Bay detention camps in Cuba. Qahtani allegedly tried to enter the United States to take part in the September 11 attacks as the 20th hijacker and was due to be onboard United Airlines Flight 93 along with the four other hijackers. He was refused entry due to suspicions that he was trying to illegally immigrate. He was later captured in Afghanistan in the Battle of Tora Bora in December 2001.

After military commissions were authorized by Congress, in February 2008, Qahtani was charged on numerous counts. In May, the charges were dropped without prejudice. New charges were filed against him in November 2008 and dropped in January 2009, as evidence had been obtained through torture and was inadmissible in court. This was the first time an official of the Bush administration had admitted any torture of detainees at Guantanamo.

The Mexico–United States border crisis is an ongoing migrant crisis in North America concerning the illegal migration of people into the United States across the Mexico-United States border. U.S. presidents Barack Obama and Donald Trump both referred to surges in migrants at the border as a "crisis" during their tenure. Following a decline in migrants crossing the border during the first Trump administration, illegal border crossings surged during the Biden administration, with over 7.2 million migrants encountered between January 2021 and January 2024, not counting gotaways. Experts have attributed the increase in attempted crossings to pent-up demand, changes in global migration patterns, a change of perceptions by migrants about the ease of crossing, and incentives for migrants to try to cross again after Title 42 expulsions. The number of migrants sent back increased as a result, though the percentage sent back decreased. Border apprehensions fell back to 2020 levels in mid-2024.

The migrants, who are mostly of Guatemalan, Salvadoran, Honduran, and Venezuelan citizenship, are reported to be escaping economic hardship, gang violence and environmental disaster in their home countries (particularly acute in Guatemala and Honduras) to seek asylum in the US. Unlike the demographic of migrants in the preceding years, an increasing proportion of current migrants arriving at the Mexico–US border are children, including unaccompanied children and from countries outside Latin America.

Presidential elections were held in the United States on November 8, 2016. The Republican ticket of businessman Donald Trump and Indiana governor Mike Pence defeated the Democratic ticket of former secretary of state Hillary Clinton and Virginia junior senator Tim Kaine, in what was considered one of the biggest political upsets in American history. It was the fifth and most recent presidential election in which the winning candidate lost the popular vote.

Incumbent Democratic president Barack Obama was ineligible to pursue a third term due to the term limits established by the Twenty-second Amendment to the U.S. Constitution. Clinton secured the nomination over U.S. senator Bernie Sanders in the Democratic primary and became the first female presidential nominee of a major American political party. Initially considered a novelty candidate, Trump presented himself as a blunt-spoken political outsider and emerged as the Republican front-runner, defeating several notable opponents, including U.S. senators Ted Cruz and Marco Rubio, as well as governors John Kasich and Jeb Bush. Trump's right-wing populist, nationalist campaign, which promised to "Make America Great Again" and opposed political correctness, illegal immigration, and many US free trade agreements, garnered extensive free media coverage due to Trump's inflammatory comments. Clinton emphasized her extensive political experience; denounced Trump and half of his supporters as "deplorable" bigots and extremists; and advocated the expansion of Obama's policies, stressing racial equality, LGBT rights, women's rights, and inclusive capitalism.

Donald Trump ran a successful campaign for the 2016 U.S. presidential election. He formally announced his campaign on June 16, 2015, at Trump Tower in New York City, initially battling for the Republican Party's nomination. On May 26, 2016, he became the Republican Party's presumptive nominee. Trump was officially nominated on July 19 at the Republican National Convention. He chose Mike Pence, the sitting governor of Indiana, as his vice presidential running mate. On November 8, Trump and Pence were elected president and vice president of the United States.

Trump's populist positions in opposition to illegal immigration and various trade agreements, such as the Trans-Pacific Partnership, earned him support especially among voters who were male, white, blue-collar, working class, and those without college degrees. Many voters in the Rust Belt, who gave Trump the electoral votes needed to win the presidency, switched from supporting Bernie Sanders to Trump after Hillary Clinton won the Democratic nomination.