Arguing in favor of his tariffs, President Donald Trump claimed on Twitter Sunday that the US had "no debt" and "a big system of tariffs" when it built "everything from Highways to the Military with CASH."

"When our Country had no debt and built everything from Highways to the Military with CASH, we had a big system of Tariffs. Now we allow other countries to steal our wealth, treasure, and jobs - But no more! The USA is doing great, with unlimited upside into the future!"

His history lesson is largely incorrect.

Facts First: The US has almost never had "no debt." It was not even close to debt-free when it created the Interstate Highway System, and the national debt spiked when the military was built up during major wars. Trump was correct that the Interstate was not financed with debt, but he did not mention where the money came from: dedicated taxes.

Let's go through Trump's tweet step by step.

"No debt": The US has been debt-free just once, in the mid-1830s, when then-president Andrew Jackson had it paid off. "There has been almost no period in US history when the federal government has been completely free of debt," said Douglas Irwin, a Dartmouth College economics professor and a prominent expert on US economic and trade history.

Trump did not say what highways he was talking about, but the US was nowhere near debt-free when the federal government approved the construction of the Interstate Highway System in 1956. The ratio of debt to Gross Domestic Product hit an all-time record, more than 100%, just after the end of World War II in 1945. Though the debt-to-GDP ratio fell in the 1950s as the economy boomed, the total debt load was about $273 billion in 1956, about $2.5 trillion in today's dollars.