Visitors are now able travel through the south loop -- accessed through the East, West and South entrances of the park -- based on an alternating license plate system, with some exceptions, the National Park Service said.
That system means vehicles with license plates ending in an odd number will be able to enter the park on odd days of the month, while even numbers (including zero) will be granted access on even days of the month, according to the service.
That's in place to slow down visitor traffic, the park service said. While there were "major backups" Wednesday morning, they were cleared at each entrance in several hours, park service officials said in a news release.
Fewer than 5,000 vehicles entered the south loop Wednesday -- a vast difference from the usual 10,000 or more cars that enter, the park service said.
"While it's too early to tell if the license plate system worked, it appears to have done its job by cutting our normal traffic counts by half," park superintendent Cam Sholly said in a statement. "We're happy to have visitors back in Yellowstone and appreciate the patience of the public and community partners as we continue working through this difficult situation."
Cars, campers and trucks lined up before sunrise Wednesday outside the south entrance of Yellowstone National Park waiting to gain entry for the first time in more than a week.
George Frey/Getty Images
The park's north loop, accessed by the North and Northeast entrances, remains closed, the service added.
The park -- which covers parts of Idaho, Montana and Wyoming -- and surrounding towns were inundated by unprecedented rainfall and flooding that caused mudslides, rockslides and other dangerous conditions, officials said. Roads had washed away in several places, while others had been impacted by mudslides and downed trees following the floods, officials reported. The heavy rain coupled with rapid snowmelt that led to flooding along the Yellowstone River was a 1 in 500-year event, the US Geological Survey (USGS) said.
Tourism industry workers around Yellowstone National Park are feeling the financial impact after historic flooding
closed the iconic park destination. CNN's Fredricka Whitfield
spoke with Shawn Darr, who runs Little Trail Creek Cabins in nearby Gardiner, Montana, about whether she and her family's business can survive, financially.
"Cars are reentering (Yellowstone National Park) this morning thanks to the hard work and dedicated efforts of many partners," Wyoming Gov. Mark Gordon said on Twitter Wednesday. "This is welcome news for our nearby communities and Wyoming tourism." The park's north loop is also expected to reopen within the next two weeks, after clean-up, repair and inspection efforts are completed, the park said in a news release earlier this week.