The verdict on the U.S.–Mexico border wall President Trump promised to construct is decidedly mixed as the year comes to a close.The “big, beautiful wall,” as Trump referred to it, reached 400 miles in length by the end of October, when the Department of Homeland Security held a ceremony hailing the achievement. But almost all construction was designed to replace existing barriers: Just nine miles of new fencing have been put up at previously empty sections of the border.This is not nothing, given that much of the existing border fencing was in need of an upgrade. Some stretches of the barrier were dilapidated, while new barriers will consist of steel bollards up to 30 feet high, with improved access roads, cameras, lighting, and other features that make breaching the barrier more difficult. However, the president’s effort to vastly expand the length of the barrier failed, and was replaced by a more modest renovation.The story of the border wall renovation reads rather like Trump’s efforts in the 1990s to develop a real-estate tract on Manhattan’s Upper West Side. What Trump proposed as “Television City,” a gleaming development by the Hudson River that would include residential buildings as well as a massive skyscraper, foundered on bureaucratic inertia, fierce opposition by residents, and Trump’s own financial problems. Trump sold the real estate parcel to investors from Hong Kong, and the resulting development, Riverside South, is an unremarkable residential complex.Similarly, the fantastical visions of a wall running along the entire southern border that Trump sold on the 2016 campaign trail have not come to fruition. The Trump administration faced a continuous stream of lawsuits aiming to halt or slow construction. Democratic lawmakers opposed any funding for construction at all. Property owners on the border also fought the administration for attempting to seize their land through declarations of eminent domain.Trump’s attempts to fund the project have ended in a gambit to circumvent Congress. During budget negotiations in fall 2018, Democrats in Congress pushed to cap funding for border operations at $1.6 billion. However, Trump refused to approve the budget if it didn’t include $5 billion in border wall funds, and the spat led to the longest federal government shutdown in U.S. history. By February 2019, the president caved and signed the budget bill without additional funding — instead, Trump resorted to declaring a national emergency at the southern border in order to divert Pentagon funds for wall construction.The Trump administration was able to turn back “caravans” of illegal immigrants arriving at the southern border that year. However, the national emergency declaration drew opposition from Republican senators including Ben Sasse (R., Neb.), concerned about a possible overreach of executive power. (Sasse ultimately voted against formally condemning Trump’s emergency declaration, arguing that the declaration did not exceed the bounds of what he considers to be an overly broad national emergency statute.)The Supreme Court in November 2020 agreed to hear a case challenging the constitutionality of the emergency declaration; it is possible that the Court will rule that the diversion of Pentagon funds to finance border-wall construction was unconstitutional.By the end of April 2020, the Trump administration had siphoned at least $10 billion in Pentagon funds for wall construction. According to planning documents obtained by the Washington Post in 2019, the administration estimated that construction of 500 miles of new barrier would average out to roughly $36 million per mile.After the budgetary maneuvers, court challenges, and other obstacles, the current barriers are scheduled to reach 450 miles by the end of the year if construction continues apace. The result is like the Riverside South development: nowhere near Trump’s grand ambitions, but nice enough.The project may sit idle during the Biden administration. Joe Biden has already promised to overhaul Trump’s immigration policies, including halting construction of the barrier once he takes office.“There will not be another foot of wall constructed on my administration,” Biden said at a meeting with black and Latino reporters in August.But it’s not yet clear if the incoming president will cease ongoing construction entirely. Federal contractors are at work on new sections of barrier, so the new administration would need to follow current regulatory law if it decided to terminate contracts.“Generally, the [contract] clauses treat the government more favorably, much more favorably, than if it was in the commercial world,” John Horan, a Georgetown University law professor specializing in government contracts, told Arizona Central in mid-November. “There is an established regulatory process to stop these contracts, if the president should so decide, in an efficient and orderly manner that will also fairly compensate the contractors for the work that has been performed.”Meanwhile, even before the election, progressive groups began urging Biden not only to stop construction but to tear down sections of barrier that have already been built.“The construction of this unlawful border wall has desecrated tribal lands, leveled wildlife preservations, and destroyed border communities,” ACLU staff attorney Dror Ladin told the Daily Beast in October. “Every unlawful mile of wall should be taken down, and the government must work with border communities to undo the damage that wall construction has already inflicted.”Just how much of the border wall is “unlawful” could be the subject of future legal battles. For example, should the Supreme Court rule that the Trump administration’s diversion of Pentagon funds toward barrier construction was unconstitutional, that could indicate that some sections of barrier were built illegally and thus give more leverage to Democrats' calling for their destruction.Of course, tearing down walls, like building them, is expensive. And rolling back Trump’s immigration policies may take time, as three people involved in developing Biden’s immigration policy have told NBC. Biden will take office amid an ongoing pandemic, and presumably vaccine-distribution efforts will be a priority.If history is any indication, government action on a border wall will remain somewhat detached from reality. Congress passed the Secure Fence Act in 2006, mandating the construction of double-layered fencing across 670 miles of the U.S.-Mexico border, but the “second layer” never materialized. Just as President Trump’s promised wall, running from the Gulf of Mexico to California, turned out to be mostly an expensive renovation of existing barriers.Now, in a Biden administration, progressives will call to tear down the refurbished barriers. But their dream of toppling Trump’s “big, beautiful wall” was made impossible by Trump’s failure to build it in the first place.