Nik Wallenda has successfully crossed Niagara Falls on a highwire strung high above the raging waters, a historic achievement for the American aerialist.

Wallenda, who hails from a long line of high-wire artists — several of whom have died during performances — started from the U.S. side at around 10:15 p.m. ET and completed it about 25 minutes after he started.

He took steady steps for most of his journey but ran the last few paces, with his safety tether trailing behind him, CBC's Adrienne Arsenault said.

The daredevil was greeted on the Canadian side by two border agents, who welcomed him to the country and inspected his passport.

"I'm not carrying anything over, I promise," a tired but happy Wallenda told the customs agents.

During his crossing, Wallenda spoke to his father through a headset and even took questions from ABC broadcasters as he made his way across the specially installed cable, which was about 550 metres long and roughly five centimetres wide.

Weather conditions were generally good, but mist swirled around Wallenda in some areas along the wire.

"The mist was so thick, so challenging, those winds hit me from every which direction, was definitely more than I expected for sure," Wallenda said, moments after reaching the Canadian side.

'Truly breathtaking'

With Friday night's success, Wallenda becomes the first tightrope walker to cross near the base of the Falls. Several others had crossed over the Niagara Gorge just downstream from the Falls more than a century ago.

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"It's an unbelievable view," Wallenda told ABC as he made his way across, dressed in red and black and wearing handcrafted suede-soled shoes. "This is truly breathtaking."

Wallenda was wearing a safety tether during the crossing, which had been the source of some controversy before the walk. ABC had insisted that Wallenda wear a tether that would prevent him from plunging to his death should he lose his balance.

Before the walk, the 33-year-old father said he was not happy about having to wear a harness, and even expressed concern that the extra weight could make his walk more difficult.

Nik Wallenda walks over Niagara Falls on a tightrope. As he crossed, Wallenda said he had an 'unbelievable view' from the cable. (Frank Gunn/Canadian Press)

But when asked about the tether shortly before the walk, he said he respected his partners and "it is what it is."

Before he stepped onto the cable, Wallenda told the American broadcaster that he was "extremely excited" to have a chance to achieve his dream.

"I am so blessed to be in the position I am, that I will be the first person in the world to walk directly over Niagara Falls on a tightrope," he said.

The tightrope walker kept a low profile most of Friday, away from the media spotlight for the first time this week.

Over the past few days, the daredevil had been practising his craft and overseeing the installation of the steel wire cable strung 60 metres above the churning waters.

Cheering crowds

Spectators were eager to get good spots ahead of the crossing. By mid-morning, two people from Buffalo, N.Y., had already staked out their watching spots.

Rick Ryskalzzyk and Veronica Bassano were the first people to park their chairs on the Canadian side, where Wallenda finished his walk.

"It's a once-in-a-lifetime event," Ryskalzzyk said.

"We were ready for it. We got a hotel room. We staked out this space last night. We're good to go."

They soon had to move from their first spots, however, to make way for about 100 television cameras from news organizations including CNN and Al-Jazeera.

Large crowds turned out to watch the spectacle, and Wallenda was greeted by cheering spectators as he neared the Canadian side.

Wallenda spent months preparing for his historic stunt — getting permits, raising funds and readying for the challenge posed by the Niagara Falls crossing.

After his walk, Wallenda remarked that he's already thinking of his next challenge, saying he has his permits in order and hopes to eventually become the first person to walk across the Grand Canyon.