UPDATED at 7:50 p.m.
The state had largely avoided the predicted traffic nightmare in the days leading up to the event, as travelers staggered their departures for the path of totality.
But they showed no such restraint after the event. Thousands of eclipse viewers hit the road in the minutes after totality, jamming key state routes.
Around 3 p.m., Google Maps predicted the drive from Madras to Portland via U.S. 26 would take more than an hour longer than usual.
The drive from Salem or Corvallis to Portland also took an extra hour. Interstate 5 near the state capital had bumper-to-bumper traffic even before the eclipse had ended.
By 7:30 p.m., traffic was lessening on Interstate 5, but it was still slow going on U.S. 97 around Madras, said Oregon Department of Transportation spokesman Thomas Fuller.
Currently, the drive from Madras to Portland via U.S. 26 is taking an extra hour or so, according to Google Maps.
There are still some delays on Interstate 5 between Woodburn and Canby, as well as some areas south of Salem, but slowing on the highway is minor compared to earlier delays, Fuller said.
Some motorists, in defiance of pleas from the Oregon Department of Transportation, parked on the side of highways to view the eclipse, apparently in hopes of making a quick exit afterward.
State officials are urging eclipse watchers to stay put and avoid clogging the highways.
The congestion lingered in the hours after the eclipse ended, but Fuller said it might well clear up by later on in the afternoon.
"The traffic wasn't as horrible as we perhaps thought it was going to be this morning, so I don't think it's going to last as long this afternoon either," he said.
The agency heard anecdotally that many people have delayed their travel to avoid the rush, while others canceled their plans altogether.
"We do have a lot of folks from out of the state who are in the area," Fuller said. We think we'll see those folks going ahead and spreading out and leaving the area. I think by mid-afternoon we'll begin to see this disperse."
ODOT also expects that many people attending festivals tied to the event will stay put. Organizers have arranged for events and entertainment to continue until Tuesday or Wednesday.
The Symbiosis Gathering festival, whose participants waited in a 15-mile backup to get in last week in what appeared to portend eclipse crowds, were trickling out in a steady flow of cars Monday, said Crook county spokeswoman Vicky Ryan.
The festival, which formally concludes Wednesday, is permitted for 30,000 attendees. But it drew at least 28,000 vehicles, and Fuller said it's now believed that 70,000 people were in attendance.
Ryan said traffic lights in the area have been adjusted to favor people going west. Ryan's heard some people are going straight to Nevada to go to Burning Man, another festival that starts Aug. 27, though not enough to significantly lighten the traffic going West.
"As these festivals let out, it's going to flood a bunch more people on Highway 97," Fuller said. "It's not a four-lane freeway. Folks are going to have to really take their time and be patient on Highway 97 for the coming days, really."
By 8 p.m. Monday, driving conditions in and around the Madras area remained bumper-to-bumper.
Gregg Kennen and his wife, Liz Kennen, spent Sunday night in Klamath Falls before heading to Madras early Monday morning to view the eclipse.
They pulled onto a side road north of the municipal airport, joining a group of eclipse chasers for the big event. Then they left around 11 a.m. to return to Klamath Falls, hoping to beat the crowd out of town.
They didn't.
Speaking to The Oregonian/OregonLive just after 6 p.m. after about 7 hours of driving, the Riverside County, California, couple had made it just over 90 miles -- about halfway to their destination.
"It's absolutely a parking lot here. It's absolutely a madhouse," Kennen said. "We knew about the traffic, but we never imagined it was going to be this."
Google Maps has predicted a three-hour trip just about the entire route, Kennen said, but there's no sign the traffic will dissipate.They stopped in Madras for food and Redmond for fuel, but Kennen said he felt sorry for others who might have skipped the opportunity because they were expecting a shorter trip.
And others on the road were clearly looking for a pit stop of another kind.
"It's crazy to see some cars who stop," he said, "You can see them running into a forest because they can't find a place."
Traffic will likely be delayed between Madras and Redmond for the next day or so, Fuller said.
For now, Fuller is urging all drivers to be patient with their commutes and to pay attention to the roads.
"There's been some talk about, 'oh it was overhyped,' but I don't think so," Fuller said. "Had we not been really preparing, people preparing when to come, preparing their vehicles, keeping a watch out and us pre-placing a lot of equipment...I think it probably would've been a lot worse than this. This about the best we can expect."
The Oregonian/OregonLive is posting updates on traffic impacts from eclipse traffic in a live blog.
-- Elliot Njus
enjus@oregonian.com
503-294-5034
@enjus
Oregonian reporters Samantha Bakall and Samantha Matsumoto contributed to this story.