In files

The border between the United States and Mexico stretches for nearly 2,000 miles from the Gulf of Mexico to the

Pacific Ocean and touches the states of California, Arizona, New Mexico and Texas. The Rio Grande runs along

1,254 miles of the border, but west of El Paso, Texas, the boundary lacks a natural geographic barrier except for a

small stretch along the Colorado River.

Approximately 700 miles of barbed wire, chain link, post-and-rail and wire mesh fencing has been erected along

the U.S.-Mexico border. The U.S. Border Patrol also utilizes thousands of cameras and underground sensors as well

as aircraft, drones and boats to monitor the boundary.

After winning its independence from Spain in 1821, Mexico stretched as far north as the Oregon Territory. The

secession of Texas in 1836, however, marked the beginning of the loss of Mexican territory that would become the

present-day U.S. Southwest.

The War with Mexico U.S. President James K. Polk captured the White House in 1844 on a pledge to fulfill America’s “Manifest Destiny”

to stretch from the Atlantic Ocean to the Pacific Ocean. Relations with Mexico deteriorated a fter the U.S. annexed

Texas in 1845. When Mexico refused an American offer to purchase California and New Mexico for $30 million,

Polk dispatched 4,000 troops into land north of the Rio Grande and south of the Nueces River claimed by both

countries.

Following a Mexican cavalry attack in the disputed territory on April 25, 1846, that left 16 American soldiers

dead or wounded, the U.S. declared war on Mexico. After a series of bloody battles and sieges, American forces

captured the Mexican capital in September 1847.

Under the 1848 Treaty of Guadalupe Hidalgo, Mexico formally recognized the American annexation of Texas

and agreed to sell more than one-third of its territory. For $15 million and the assumption of certain damage claims,

the U.S. purchased more than a half million square miles that would encompass all or most of the future states of

California, Arizona, New Mexico, Nevada and Utah as well as portions of present-day Colorado, Wyoming,

Oklahoma and Kansas.

The Establishment of the U.S.-Mexico Border The modern border took shape following the Mexican-American War. While the Rio Grande formed the dividing

line between Texas and Mexico, the border originally moved west from El Paso on a straight line to the Gila River

and then on another straight line to the Pacific Ocean south of San Diego. Following the Gadsden Purchase of 1853,

the borders of Arizona and New Mexico moved further south from the Gila River.

A team of surveyors, soldiers and officials from both countries staked out the border from El Paso to Tijuana.

According to Rachel St. John, an associate professor of history at UC Davis and author of Line in the Sand: A

History of the Western U.S.-Mexico Border, the joint boundary commission underestimated the cost and time it

would take to complete the project through such an inhospitable terrain of mountains, canyons and desert. Not until

the late 1850s did the boundary commission complete its work.

U.S. Immigration Policy There were no federal limits on immigration in the decades following the Mexican -American War as citizens from

both countries passed freely across the border. It was Chinese immigrants, not Mexicans, that American authorities

and vigilante groups first sought to keep from illegally crossing its southern border after the passage of the Chinese

Exclusion Act of 1882. “One of the

ways that immigrants from China

would try to get across the border is

to learn a few words of Spanish and

disguise themselves as Mexican,” St.

John says.

“Restrictions on the movement of

Mexican citizens were not particu-

larly enforced by the U.S. govern-

ment until the decade of the Mexican

Revolution in the 1910s when large

numbers of refugees came to escape

the war and there was a large demand

for Mexican labor,” St. John says.

Following Mexican revolutionary

Pancho Villa’s deadly raid on

Columbus, New Mexico, in 1916 and

the subsequent publication of the

Zimmerman Telegram proposing a

World War I military alliance

between Mexico and Germany, the

U.S. tightened border security and

deployed soldiers to patrol the

boundary along with the Texas

Rangers and government-sanctioned

“home guards.”

According to St. John, the U.S.

Bureau of Animal Industry erected

the first fence along the frontier in 1909 to stop the trans -border movement of cattle. Border towns erected fences

during the 1910s, but less as a physical barrier to entry than to denote the boundary line and channel people into

designated crossing points. The U.S. began the installation of border fences to restrict the movement of unlawful

immigrants and drugs in 1993 when President Bill Clinton mandated the construction of a 14-mile barrier between

San Diego and Tijuana. The Secure Fence Act of 2006 authorized the construction of 700 miles of border fencing

and vehicle barriers, which was completed in 2011.

Future Plans for the Border Approximately 11.6 million Mexican immigrants resided in the U.S. in 2016, about half of them in the country

illegally, according to Pew Research Center estimates.

The centerpiece of President Donald Trump’s

immigration plan is the construction of an “impene-

trable, physical, tall, powerful, beautiful, southern

border wall,” but the project faces funding, environ-

mental and eminent domain obstacles.

While Trump asserts the construction of a new

1,000 miles of wall as high as 55 feet tall through

remote, mountainous terrain can be built for $18

billion, an analysis published in MIT Technology

Review estimates the cost to be $40 billion. The

Mexican government stated that it would not pay for

the wall’s construction, as Trump repeatedly pledged

during the 2016 presidential campaign, and Congress

contributed only $1.6 billion to the project in March

2018.

In April 2018, President Donald Trump ordered

National Guard troops deployed to the border until

further progress is made on construction of the wall.

The move was not unprecedented as his predecessors

George W. Bush and Barack Obama also sent the

National Guard to assist with border security.

Klein, Christopher. (04/17/2018) Everything You Need to Know About the Mexico-United States Border. The History Channel Website located at: https://www.history.com/news/everything-you-need-to-know-about-the-mexico-united-states-border.

Map of Mexico with the new boundaries established by the Treaty of Guadalupe,

1848. (Credit: Dea G. Dagli Orti/De Agostini/Getty Images)

A sign is posted near the US and Mexico border warning

drivers of immigrants crossing the freeway in San Ysidro, CA

in 2006, just before signing of the Secure Fence Act. (Credit:

Hector Mata/AFP/Getty Images)