After viewing the wall prototypes in an area of the border heavily cordoned off and far from the rallies on the USA side, addressed the military at Marine Corps Air Station Miramar before flying to Los Angeles and attend a high-dollar fundraiser in Beverly Hills.
This visit to California comes just one week after the Trump administration chose to sue the state of California over immigration laws, as reported by the New York Times. The Trump administration is now battling with California about its refusal to help federal agents detain undocumented immigrants in the United States.
"I have a message for you straight from the heart of the American people, and you know what that is".
"And if you don't [have] safety, meaning if you don't have this kind of wall, the drugs are pouring through in California, can't do it", he said.
"We are working with all of our local and federal partners to ensure that all security safeguards are in place for the president's visit, both along his route of travel and at the locations where events will take place", Los Angeles police Detective Meghan Aguilar said.
Trump addressed Marines and other service members at an air base in San Diego after visiting his border wall prototypes.
San Diego's Republican mayor criticised Trump's planned short visit, saying the president won't get a full picture of the city.
U.S. and Mexican authorities appeared to be collaborating closely on security measures before the president's visit.More news: Lonzo Ball praises Julius Randle as Lakers' 'enforcer'
Trump continued, promising to uphold his administration's policy of "peace through strength" and the "largest military buildup since Ronald Regan".
Trump's vow to build the wall was one of his key pre-election promises.
Last month, the Trump administration criticized a number of immigration reform proposals in Congress - almost all of which included funding for the border wall and border security. "They don't tell you that". In the evening, Trump will attend a GOP fundraiser in Beverly Hills. In a letter Monday, he invited Trump north to the Central Valley to tour the bridges and viaducts being built for the state's high-speed rail line.
This isn't Trump's first visit to the border.
The hundreds expected at the San Ysidro rally also held up California immigration policies as ones that should be emulated on a national level - the same policies that have raised the ire of the Trump administration.
Ahead of his arrival, the president tweeted that "thousands of risky, violent criminal aliens are released" as a result of California's immigration sanctuary policies.
On the other side of the border, in Tijuana, Mexico, residents laughed off the idea that the monolithic slabs will stop desperate immigrants.
"We may even have a 'space force, '" Trump said.
After construction was completed, the prototypes were tested on several fronts, including on withstanding breaches, climbing, digging, their ability to slow down and stop border traffic, and whether they are safe for Border Patrol agents.