DOUGLAS, ARIZONA (NYTIMES) - Four years ago, President Donald Trump took office with a pledge to build a towering wall on America's border with Mexico - a symbol of his determination to halt immigration from countries to the south and build a barrier that would long outlast him.

President-elect Joe Biden has said he hopes to halt construction of the border wall, but the outgoing administration is rushing to complete as much wall as possible in its last weeks in power, dynamiting through some of the border's most forbidding terrain.

The breakneck pace at which construction is continuing all but assures that the wall, whatever Mr Biden decides to do, is here to stay for the foreseeable future, establishing a contentious legacy for Mr Trump in places that were crucial to his defeat.

In southeastern Arizona, the continuing political divisiveness around the President's signature construction project has pitted rancher against rancher and neighbour against neighbour in a state that a Democratic presidential candidate narrowly carried for the first time in decades.

The region is emerging as one of the Trump administration's last centres of wall building as blasting crews feverishly tear through the remote Peloncillo Mountains, where ocelots and bighorn sheep roam through woodlands of cottonwoods and sycamores.

"Wildlife corridors, the archaeology and history, that's all being blasted to oblivion or destroyed already," said Mr Bill McDonald, 68, a fifth-generation cattleman and former lifelong Republican who voted for Mr Biden.

"Tragedy is the word I use to describe it."

While the President-elect has said he will halt new wall construction, other immigration priorities like ending travel bans, accepting more refugees and easing asylum restrictions are eclipsing calls to tear down portions of the wall that already exist, with one adviser calling the wall a "distraction".

Customs and Border Protection officials are still rushing to meet Mr Trump's mandate of 724.2km of new wall construction during his term, nearly doubling the rate of construction since the start of the year.

The administration had built 647km of wall as of Nov 13.

Of that, about 40km had no barrier before Mr Trump took office.

The rest replaced much smaller, dilapidated sections of wall, or sections that had only vehicle barriers, which border officials say did not deter migrants crossing on foot.