Here are the facts:
- The illegal immigrant population in the United States peaked at 12.2 million and declined to 10.7 million by 2016, according to the Pew Research Center.
- 66 percent of illegal immigrants in the U.S. have been here longer than 10 years. 18 percent have been here less than 5 years, also according to Pew.
- From 2008 to 2015 1.1 million illegal immigrants "entered without permission" (EWI) which means crossing the land border without permission. 2 million illegal immigrants had valid visas and then overstayed their term, according to the Center for Migration Studies.
- From 2008 to 2015, 1.7 million illegal immigrants left the U.S. to return to Mexico and 900 thousand left Mexico to enter the U.S. illegally.
- The so-called "Northern Triangle" countries of Central America are Guatemala, Honduras and El Salvador. They are the only nations showing a significant spike in illegal immigration to the U.S., due largely to an epidemic of violent crime and lawlessness in the region, according to Pew.
- Homeland Security statistics show a decline in apprehensions along the Mexican border for the last 20 years. Apprehensions topped out at more than 1.6 million in 2000 and sinking to around 300 thousand in 2017.
- The bulk of heroin and methamphetamine across the border in trucks and personal vehicles, using secret compartments or hiding the drugs amidst legitimate products, according to the National Drug Threat Assessment in 2015. Marijuana and cocaine smuggling is on the decline.
- In 2017 the State Department said there was, "no credible information that any member of a terrorist group has traveled through Mexico to gain access to the United States."
- The U.S. has 650 miles of various types of walls and fences along the border. Some of it to keep pedestrians from crossing, with others meant to stop vehicles. Much of the rest of the border is delineated by the Rio Grande and its canyons and bluffs.
- A portion of the border has been kept fence-less to protect the habitat of the last North American Jaguars, an endangered species.