Trump made the announcement from the Oval Office in an event that began after 2 p.m. ET. A White House official told CNBC, speaking on condition of anonymity ahead of the event, that the plant aims to begin production in 2030. The Wall Street Journal first reported the news earlier that morning.

The timing lands just weeks before the November midterm election, a race expected to hinge partly on how Americans view Trump's handling of the economy. A $15 billion manufacturing investment, and the jobs that typically come with a project of that size, gives the administration a concrete talking point heading into a stretch where economic sentiment could decide close races.

For Iowa, the plant represents a major industrial bet years before it produces a single ton of steel. That payoff, though, lands long after this election is over, even as the political messaging around it starts now.

Mesabi Metallics hasn't laid out how many jobs the plant would create or exactly where in Iowa it would sit. Five years is a long wait for a project announced in a five-minute Oval Office photo op.