The US media reported that 12 million people lived in the path of the total eclipse, while 200 million within a day's driving distance from the band.
A total eclipse is not a rare occurrence, appearing on Earth about every 18 months, but a total eclipse that stretches from coast to coast in the USA is rarer, with the last one taking place almost a century ago and the next one scheduled for 2045. "It's going to be probably the most people we've ever seen in OR".
Clouds might still interfere, although most - not all - weather services are predicting clear skies.
In neighboring Idaho, up to 400,000 people could show up. What a gorgeous day!
Astronomers were giddy with excitement. Jim Todd, a director at the Oregon Museum of Science and Industry, told a crowd of thousands at an amphitheater in Salem, Oregon, as the moon took an ever-bigger bite out of the sun.
Hundreds of amateur astronomers converged on Casper, Wyoming. He has seen full solar eclipses before, but never so close to home, making this one extra special. "It makes you feel insignificant, like you're just a speck in the whole scheme of things". He said he was "expecting to have a real sense of connection with the heavens".
Officials have also been grappling with the possibility that cloudy weather, closed roads or coastal fog could prompt eclipse-watchers to change plans at the last minute, throwing traffic into chaos.
"I'm about to fight this man for a window seat", Lightfoot said, referring to a fellow NASA official.
The Earth, moon and sun line up perfectly every one to three years, briefly turning day into night for a sliver of the planet.
A string of tail lights can be seen on the Interstate 5 to the direction of Salem, Oregon, before 5 o'clock on Monday morning, as people from all over the world rushed to this small city for a first glimpse of a once-in-a-century total eclipse.
One video from NASA showed the International Space Station pass in front of the sun during the eclipse.
Traffic stalled in central OR on Wednesday as 30,000 people poured in for a large festival near the town of Prineville, creating miles-long backups on US 26.
The total solar eclipse touched down on the OR coast between at 1:15 p.m. EST (10:15 a.m. PT).
Shawnee National Forest in southern IL saw the longest stretch of darkness: 2 minutes and 44 seconds.
Citizen scientists also planned to monitor animal and plant behavior as daylight turned into twilight and the temperature dropped.
A growing wildfire in the central part of the state Friday complicated plans, and authorities ordered mandatory evacuations for about 1,500 people just as thousands more were expected to start arriving.
Ryan Jackson, the creative director of the Montreal Planetarium in Canada, had set up almost 10 cameras pointing towards various directions in the sky, forming a circle which he said could help him capture the moment when the sky darkened.
Kim Kniseley drove overnight from Roanoke, Virginia, arriving in Madisonville, Tennessee, before dawn Monday to get a parking spot at Kefauver Park, where by sunrise dozens of folks had claimed benches and set up tents. "We're not going to be completely overcast and not see anything".
Scientists warned people not to look into the sun without protection, except when the sun is 100 percent covered. Otherwise, to avoid eye damage, keep the solar specs on or use pinhole projectors that can cast an image of the eclipse into a box.
According to media reports, distraction caused by the eclipse will cost USA companies 700 million US dollars but other analysts argued with all the tourism and consumption related to the event, the economy has actually benefitted from the eclipse. The next coast-to-coast one will not be until 2045.