He vowed to improve America’s standing in the world, citing his experience as a negotiator, and repeated a call to repeal and replace the Affordable Care Act, though the details of this endeavor remained murky.

A supporter suggested a name from the rafters: DonaldCare.

“Thank you!” Mr. Trump said. “We’ll call it DonaldCare.”

His closing remarks drew upon the mantra etched across his signature campaign hat.

“You’re going to say to your children, and you’re going to say to anybody else, that we were part of a movement to take back our country,” he said. “And we will make America great again.”

Earlier, some in the crowd had become a bit restless when Mr. Trump remained out of sight for about 30 minutes after the announced start time for his speech.

One speaker, who had just introduced him, offered a reason for the delay: “He’s back there,” she said, gesturing offstage, “doing exceptional things.”

Before the event, several people sought to replicate what they saw as Mr. Trump’s capitalist spirit. Working the plaza, Rick Snowden and Janet Newlon moved to sell the last of their Trump swag: 24 hats, 36 visors and 100 buttons, driven here from Tennessee.

Mr. Snowden is an entrepreneur, he said. Just like Mr. Trump.

“It’s very attractive to think of a candidate who’s not beholden,” Mr. Snowden said. He added that the gathering called to mind a Barry Goldwater rally he had attended in 1964.