SAN DIEGO (AP) — A jackhammer reduced prototypes of President Donald Trump's prized border wall into piles of rubble Wednesday, a quick ending to an experiment that turned into a spectacle at times.

The four concrete and four steel panels, spaced closely together steps from an existing barrier separating San Diego and Tijuana, Mexico, instantly became powerful symbols associated with the president and one of his top priorities when they went up 16 months ago.

For Trump's allies, the towering models were a show of his commitment to border security and making good on a core campaign promise. For...