Shops reported a run on telescopes as the public sought out Mars, which was an estimated 55.76 million kilometres (34.65 million miles) from Earth.
The two planets have not been so close for 60,000 years and for US experts and the public it was a way to have fun, discover the universe and make money.
"You don't have to know about astronomy, you just look to the southeast, you can't miss it. It's bright yellow orange," declared Alan MacRobert, a senior editor at Sky and Telescope magazine who said it was impossible to tell how many events had been organised.
The Westchester Amateur Astronomers club in New York state held it's "Mars Party" on Wednesday but warned people to be ready to wait until 10:00 pm or later to get a glimpse.
The Griffith Park Observatory in Los Angeles expected "thousands" to attend a series of Mars parties when it throws open its telescopes to the public from Wednesday until the end of September, according to Griffith astronomer John Mosley.
Griffith director Ed Krupp said "it's certainly a red-letter day for the Red Planet. It's that chance that it might harbour life that captures people's imagination."
On Tuesday night, members of the Tar River Astronomers Club in North Carolina set up nine telescopes for the public. And many people who went along were looking up into space for the first time.
"It was exciting to see it that big," said Lewis Thompson, vice president of the club. "We saw the ice cap on (Mars) south pole, the dark spots created by a huge asteroid."
Shawn Bryan, the owner of Boston Telescopes in Massachusetts state, said the Mars phenomenon had been "fantastic" for him as stocks have nearly run out.
"Every single day we sell telescopes to people who want to see Mars. Our sales have doubled in August, even tripled."
An average telescope costs about 500 dollars but Bryan sells versions costing between 100 and 16,000 dollars.
John Clarke, an astronomy professor at Boston University, said "there's a great deal of fascination and excitement in the United States" over Mars moving closer, even if only briefly.
"There's a whole history about it, the God of War, the idea of life out there, the fact that it is the closest to earth, that we might some day be able to live there," said Clarke.
The image of the "Little Green Men" on Mars was first raised by Percival Lowell, an American astronomer, at the end of the 19th century describing the canals that he thought had been made by Martians trying to conserve their water.
Fears of an attack by Martians were spread when a version of H.G. Wells' "War of the Worlds" was broadcast on US radio in 1938, causing widespread panic because it was considered so lifelike.
Ray Bradbury, the acclaimed writer of "The Martian Chronicles" and other science fiction works, said last Saturday during a party for his 83rd birthday organized by The Planetary Society: "One night, 100 years from now, a youngster will stay up late reading 'The Martian Chronicles' with a flashlight under his blanket on the Red Planet. That's the dream I have and that's the reason I'm here."