U.S. Customs and Border Protection solicited bids previous year using existing border security funding to build eight wall prototypes and awarded contracts to six private companies for mock-ups that are each 30 feet long and as much as 30 feet high.
The Republican brought a tough message on immigration to California during his first visit as USA president to the heavily Democratic state that has served as a base of resistance to many of his policies.
Trump's solo flight suggests the political risk he brings to state Republicans given his low popularity in California.
Standing beside the prototypes, as United States border patrol agents rode nearby on horseback, Mr Trump discussed the merits of various designs with border officials, his chief of staff, John Kelly, and Homeland Security Secretary Kirstjen Nielsen. Kevin Faulconer said a popular cross-border airport terminal connecting San Diego and Tijuana shows that "building bridges has worked wonders". "Many of them were criminals with criminal records and very risky people".
During his visit, the president reiterated the importance he granted to that work, one of his main promises during his campaign, because if the wall is not built, 'we will not have a country, ' he said. Trump will inspect eight prototypes for his future wall project before meeting Marines later in the day.
He added: "The state of California is begging us to build walls in certain areas, they won't tell you that, but we said no we won't do it until we build the whole wall".
The two sides were separated by a heavy presence of police officers in helmets and riot gear, but the rallies were peaceful.
At Our Lady of Mount Carmel at noon in San Ysidro, elected officials will rally with interfaith leaders to urge protection of the state's immigrant communities. Trump is scheduled to visit San Diego, Tuesday, setting foot in California for his first time as president.
The visit comes amid increasing tensions between the Trump administration and the left-leaning state over differing views on immigration.
But Trump seemed optimistic that a change in leadership following the Mexican election in July could lead to a more favorable set of circumstances.
As expected, President Trump's tour of his eight border wall prototypes in San Diego was the highlight of his first presidential visit to solid-blue California.
After leaving the border, Trump basked in the cheers of U.S. Marines in Miramar, pointing to his work to build up the nation's military.
Trump's visit comes just days after his Justice Department sued to block California laws created to protect people living in the USA illegally.
"We're going out to the wall", Trump told reporters as he departed the White House.
Tractor-trailer rigs have been parked along the USA side, blocking the view from Mexico. No information was released about his overnight accommodations, but Los Angeles police were seen staging Tuesday morning in the vicinity of the InterContinental Los Angeles Downtown Hotel near Wilshire Boulevard and Figueroa Street, and some streets in the area were closed. Trump has insisted Mexico pay for the wall.
"I'll take you to East L.A. and Boyle Heights, " he said.
The hulking prototypes can be seen from across the border in Tijuana, where residents are not overly impressed with the real estate tycoon, who launched his presidential campaign calling Mexicans "criminals" and "rapists". The mayor's office said Faulconer has been clear in his opposition to walls along the border but he did not want to blacklist companies involved in the construction of the prototypes. The event was organized in part by the ACLU of San Diego and Imperial Counties.
The video ends with Trump grinning, two thumbs up, as he's posing for a picture with border agents and Homeland Security officials. "It's something that he's going to continue to push for".