Long US-Mexican border defies attempts to close it off

Central American migrants who ran into walls of security personnel, razor wire and tear gas at the US border in Tijuana, Mexico on Sunday chose possibly the hardest place to pass.The 2,000 mile (3,200 kilometer) border from the Pacific Ocean to the Gulf of Mexico has long defied efforts to seal it off, due to a mix of politics and sheer geography.President Donald Trump has demanded the whole border be fenced, a near-impossible task.