Of all the imbroglios to mar Hoover's first, extended encounter with the Congress, the tariff was perhaps the most costly. It dragged on incessantly, it brought out the worst of the legislators, and it highlighted Hoover's weakness as a leader - all in service of a bill that nobody much liked in the end.

The final version of the tariff bill authored by Utah senator Reed Smoot and Representative Willie Hawley of Oregon, engaged in wholesale rate hikes covering 887 specific products - a far cry from the limited revision first proposed by Hoover. After winning House approval in May, the bill engendered a groundswell of protest, including a public letter from 1,028 economists demanding a Hoover veto. But that was impossible; having stood by as the bill made it tortuous way through Congress, the president could hardly turn its back on a measure endorsed by a clear majority of his own party.

The undersigned American economists and teachers of economics strongly urge that any measure which provides for a general upward revision of tariff rates be denied passage by Congress, or if passed, be vetoed by the President.

We are convinced that increased protective duties would be a mistake. They would operate, in general, to increase the prices which domestic consumers would have to pay. By raising prices they would encourage concerns with higher costs to undertake production, thus compelling the consumer to subsidize waste and inefficiency in industry. At the same time they would force him to pay higher rates of profit to established firms which enjoyed lower production costs. A higher level of protection, such as is contemplated by both the House and Senate bills, would therefore raise the cost of living and injure the great majority of our citizens.

Few people could hope to gain from such a change. Miners, construction, transportation and public utility workers, professional people and those employed in banks, hotels, newspaper offices, in the wholesale and retail trades, and scores of other occupations would clearly lose, since they produce no products which could be protected by tariff barriers.

The vast majority of farmers, also, would lose. Their cotton, corn, lard, and wheat are export crops and are sold in the world market. They have no important competition in the home market. They can not benefit, therefore, from any tariff which is imposed upon the basic commodities which they produce. They would lose through the increased duties on manufactured goods, however, and in a double fashion. First, as consumers they would have to pay still higher prices for the products, made of textiles, chemicals, iron, and steel, which they buy. Second, as producers, their ability to sell their products would be further restricted by the barriers placed in the way of foreigners who wished to sell manufactured goods to us.

Our export trade, in general, would suffer. Countries can not permanently buy from us unless they are permitted to sell to us, and the more we restrict the importation of goods from them by means of ever higher tariffs the more we reduce the possibility of our exporting to them. This applies to such exporting industries as copper, automobiles, agricultural machinery, typewriters, and the like fully as much as it does to farming. The difficulties of these industries are likely to be increased still further if we pass a higher tariff. There are already many evidences that such action would inevitably provoke other countries to pay us back in kind by levying retaliatory duties against our goods. There are few more ironical spectacles than that of the American Government as it seeks, on the one hand, to promote exports through the activity of the Bureau of Foreign and Domestic Commerce, while, on the other hand, by increasing tariffs it makes exportation ever more difficult. President Hoover has well said, in his message to Congress on April 16, 1929, “It is obviously unwise protection which sacrifices a greater amount of employment in exports to gain a less amount of employment from imports.”

We do not believe that American manufacturers, in general, need higher tariffs. The report of the President’s committee on recent economics changes has shown that industrial efficiency has increased, that costs have fallen, that profits have grown with amazing rapidity since the end of the war. Already our factories supply our people with over 96 percent of the manufactured goods which they consume, and our producers look to foreign markets to absorb the increasing output of their machines. Further barriers to trade will serve them not well, but ill. Many of our citizens have invested their money in foreign enterprises. The Department of Commerce has estimated that such investments, entirely aside from the war debts, amounted to between $12,555,000,000 and $14,555,000,000 on January 1, 1929. These investors, too, would suffer if protective duties were to be increased, since such action would make it still more difficult for their foreign creditors to pay them the interest due them.

America is now facing the problem of unemployment. Her labor can find work only if her factories can sell their products. Higher tariffs would not promote such sales. We can not increase employment by restricting trade. American industry, in the present crisis, might well be spared the burden of adjusting itself to new schedules of protective duties.

Finally, we would urge our Government to consider the bitterness which a policy of higher tariffs would inevitably inject into our international relations. The United States was ably represented at the World Economic Conference which was held under the auspices of the League of Nations in 1927. This conference adopted a resolution announcing that “the time has come to put an end to the increase in tariffs and move in the opposite direction.” The higher duties proposed in our pending legislation violate the spirit of this agreement and plainly invite other nations to compete with us in raising further barriers to trade. A tariff war does not furnish good soil for the growth of world peace.

Approved by President Herbert Hoover despite the appeals of over a thousand leading economists to reject it, the Hawley-Smoot Tariff raised the tariffs of the Fordney-McCumber Act and set import duties at some of the highest levels in American history. Proposed by Representative Willis Hawley of Oregon and Senator Reed Smoot of Utah, the tariff was intended to help particularly agriculture in the face of falling prices. However, it was extended to cover many aspects of manufacturing industry. Its effects were disastrous as foreign nations introduced their own retaliatory duties leading to a further fall in American and world trade and only increasing the impact of the Depression.

The really bad economic idea during the Great Depression, put forward by the Republican senator for Utah Reed Smoot and the Oregon representative Willis Hawley, was to raise taxes on more than 20,000 imported goods to record levels. Ignoring the widespread opposition of economists, the politicians made bold claims as to how the new legislation would transform America's economy. Hawley predicted that it would bring "a renewed era of prosperity". Frank Crowther, a New York Republican representative, said that "business confidence will be immediately restored. We shall gradually work out of the temporary slump we have been in for the last few months... We shall dissipate the dark clouds of your gloomy prophecy with the rising sunshine of continued prosperity."

In May 1930, 1,028 economists signed a petition asking President Herbert Hoover to veto the legislation, but the act became law just a couple of weeks later. Unfortunately, the Republican politicians' predictions were wide of the mark and the economy sank deeper into depression. The Smoot-Hawley Tariff proved to be the most damaging piece of trade legislation in US history.

Other governments are to an ever-increasing extent winning their share of international trade by negotiated reciprocal trade agreements. If American agricultural and industrial interests are to retain their deserved place in this trade, the American government must be in a position to bargain for the place with other governments by rapid and decisive negotiation based upon a carefully considered program, and to grant with discernment corresponding opportunities in the American market for foreign products supplementary to our own. If the American government is not in a position to make fair offers for fair opportunities, its trade will be superseded. If it is not in a position at a given moment rapidly to alter the terms on which it is willing to deal with other countries, it cannot adequately protect its trade against discriminations and against bargains injurious to its interests.

What captain of industry or what union leader in this country really yearns and is eager to return to the days of Smoot-Hawley? For the world of you-know-what-deep depressions, rampant unemployment, low profits, if any and, generally, losses.

As America inches towards a potential trade war over steel prices can Donald Trump hear whispering voices? Alone in the Oval Office in the wee dark hours, illuminated by the glow of his Twitter app, does he feel the sudden chill flowing from those freshly hung gold drapes? It is the shades of Smoot and Hawley.

Willis Hawley and Reed Smoot have haunted Congress since the 1930s when they were the architects of the Smoot-Hawley tariff bill, among the most decried pieces of legislation in US history and a bill blamed by some for not only for triggering the Great Depression but also contributing to the start of the second world war.

Pilloried even in their own time, their bloodied names have been brought out like Jacob Marley's ghost every time America has taken a protectionist turn on trade policy. And America has certainly taken a protectionist turn.

Successful presidents including Barack Obama and Bill Clinton have campaigned on the perils of free trade only to drop the rhetoric once installed in the White House. Trump called Mexicans "rapists" on the campaign trail. And China? "There are people who wish I wouldn't refer to China as our enemy. But that's exactly what they are," Trump said.

As commander-in-chief he has shown no signs of softening and this week took major action announcing steel imports would face a 25% tariff and aluminium 10%.

Canada and the EU said they would bring forward their own counter-measures. Mexico, China and Brazil have also said they are considering retaliatory steps.

Trump doesn't seem worried. "Trade wars are good," he tweeted even as the usually friendly Wall Street Journal thundered that "Trump's tariff folly" was the "biggest policy blunder of his Presidency".

It is not his first protectionist move. In his first days in office the president has vetoed the Trans-Pacific Partnership (TPP), the biggest trade deal in a generation, said he will review the North American Free Trade Agreement (Nafta), a deal he has called "the worst in history", and had his visit with Mexico's president cancelled over his plans to make them pay for a border wall.

Free traders may have become complacent after hearing tough talk on trade from so many presidential candidates on the campaign trail only to watch them furiously back-pedal when they get into office, said Dartmouth professor and trade expert Douglas Irwin. "Unfortunately that pattern may have been broken," he says. "It looks like we have to take Trump literally and seriously about his threats on trade."

Not since Herbert Hoover has a US president been so down on free trade. And Hoover was the man who signed off on Smoot and Hawley's bill.

Hawley, an Oregon congressman and a professor of history and economics, became a stock figure in the textbooks of his successors thanks to his partnership with the lean, patrician figure of Senator Reed Smoot, a Mormon apostle known as the "sugar senator" for his protectionist stance towards Utah's sugar beet industry.

Before he was shackled to Hawley for eternity Smoot was more famous for his Mormonism and his abhorrence of bawdy books, a disgust that inspired the immortal headline "Smoot Smites Smut" after he attacked the importation of Lady's Chatterley's Lover, Robert Burns' more risqué poems and similar texts as "worse than opium … I would rather have a child of mine use opium than read these books."

But it was imports of another kind that secured Smoot and Hawley's place in infamy.

The US economy was doing well in the 1920s as the consumer society was being born to the sound of jazz. The Tariff Act began life largely as a politically motivated response to appease the agricultural lobby that had fallen behind as American workers, and money, consolidated in the cities.

Foreign demand for US produce had soared during the first world war, and farm prices doubled between 1915 and 1918. A wave of land speculation followed and farmers took on debt as they looked to expand production. By the early 1920s farmers had found themselves heavily in debt and squeezed by tightening monetary policy and an unexpected collapse in commodity prices.

Nearly a quarter of the American labor force was then employed on the land, and Congress could not ignore heartland America. Cheap foreign imports and their toll on the domestic market became a hot issue in the 1928 election. Even bananas weren't safe. Irwin quotes one critic in his book Peddling Protectionism: Smoot Hawley and the Great Depression: "The enormous imports of cheap bananas into the United States tend to curtail the domestic consumption of fresh fruits produced in the United States."

Republicans called protective tariffs "essential for the continued prosperity of the country" and Hoover, who said agriculture was "the most urgent economic problem" facing the nation, said "an adequate tariff is the foundation of farm relief".

Hoover won in a landslide against Albert E Smith, an out-of-touch New Yorker who didn't appeal to middle America, and soon after promised to pass "limited" tariff reforms.

Hawley started the bill but with Smoot behind him it metastasized as lobby groups shoehorned their products into the bill, eventually proposing higher tariffs on more than 20,000 imported goods.

Siren voices warned of dire consequences. Henry Ford reportedly told Hoover the bill was "an economic stupidity".

Critics of the tariffs were being aided and abetted by "internationalists" willing to "betray American interests", said Smoot. Reports claiming the bill would harm the US economy were decried as fake news. Republican Frank Crowther, dismissed press criticism as "demagoguery and untruth, scandalous untruth".

In October 1929 as the Senate debated the tariff bill the stock market crashed. When the bill finally made it to Hoover's desk in June 1930 it had morphed from his original "limited" plan to the "highest rates ever known", according to a New York Times editorial.

The extent to which Smoot and Hawley were to blame for the coming Great Depression is still a matter of debate. "Ask a thousand economists and you will get a thousand and five answers," said Charles Geisst, professor of economics at Manhattan College and author of Wall Street: A History.

What is apparent is that the bill sparked international outrage and a backlash. Canada and Europe reacted with a wave of protectionist tariffs that deepened a global depression that presaged the rise of Hitler and the second world war. A myriad other factors contributed to the Depression, and to the second world war, but inarguably one consequence of Smoot-Hawley in the US was that never again would a sitting US president be so avowedly anti-trade. Until today.

Franklin D Roosevelt swept into power in 1933 and for the first time the president was granted the authority to undertake trade negotiations to reduce foreign barriers on US exports in exchange for lower US tariffs. The backlash against Smoot and Hawley continued to the present day. The average tariff on dutiable imports was 45% in 1930; by 2010 it was 5%.

The lessons of Smoot-Hawley used to be taught in high schools, said Geisst. Presidents from Lyndon Johnson to Ronald Reagan have enlisted the unhappy duo when facing off with free trade critics. "I have been around long enough to remember that when we did that once before in this century, something called Smoot-Hawley, we lived through a nightmare," Reagan, who came of age during the Great Depression, said in 1984.

They even got a mention in Ferris Bueller's Day Off when actor Ben Stein's teacher bores his class with it. "I don't think the current generation are taught it. It's in the past and we are more interested in the future," said Geisst.

But that might be about to change. "The main lesson is that you have to worry about what other countries do. Countries will retaliate," said Irwin. "When Congress was considering Smoot-Hawley in the 1930s they didn't consider what other countries might do in reaction. They thought other countries would remain passive. But other countries don't remain passive."

The consequences of a trade war today are far worse than in the 1930s. Exports of goods and services account for about 13% of US gross domestic product (GDP) – the broadest measure of an economy. It was roughly 5% back in 1920.

"The US is much more engaged in trade, it's much more a part of the fabric of the country, than it was in the 1920s and 1930s. That means the ripple effects are widespread. Many more industries will be hit by it and the scope for foreign retaliation, which in the case of Smoot-Hawley was quite limited, is going to be much more widespread if a trade war was to start," said Irwin.

"When you start talking about withdrawing from trade agreements or imposing tariffs of 35%, if you are doing that as a protectionist measure, that would be blowing up the system."

That the promise of "blowing up the system" got Trump elected may be why the ghosts of Smoot and Hawley are once again walking the halls of Congress.