In all, cities across the region, from Minneapolis down to New Orleans, have been slammed by heavy rain and flooding.
And it's not over yet. More heavy rain is in the forecast for today, and over 10 million remain under flood warnings from Oklahoma into Kansas, Missouri and Illinois. The greatest flash flood potential will be from Texas into Arkansas, where 2 to 4 inches of rainfall will be common.
Here's a look at the extent of this flooding across the region.
The hardest hit areas will likely be along the Arkansas River, with a crest today in Tulsa near the record for the river. Floodwaters from the Arkansas River have inundated homes outside Tulsa, such as in these photos from May 23 in Sand Springs.
Debbie Chavez, who has lived with her family in Sand Springs for 24 years, said evacuation started after the water was in the driveway of her neighbors' house last week. She took the below photos of the rising water.
Tulsa Mayor G.T. Bynum warned his city to prepare for the "worst case scenario we've had" in the city's history of flooding.
US Rep. Kevin Hern, who represents parts of Tulsa County and Sand Springs, said he was extremely concerned about the aging levees in his district.
"The devastation from the Arkansas River flooding is real, and the continued risk to citizens and businesses is equally as real," he said.
The Arkansas River, already rising, will reach near-record or record levels -- above 40 feet in some areas -- Thursday afternoon, officials said.
"This is looking to be record-breaking all along the Arkansas River, and this is something we have never seen before," state emergency management spokeswoman Melody Daniel said.
In Fort Smith, for example, people stood and looked out over the flooded Massard Creek last Saturday.
While in Chaffee Crossing, volunteers filled sand bags in a parking lot, readying to distribute them to flood prone areas around homes.
In Logan County, the sheriff posted photos of a levee along Highway 309 that has overtopped due to flooding.
Arkansas Gov. Asa Hutchinson announced that he'd conduct an aerial tour Thursday out of Fort Smith.
"This is a flood of historic magnitude, it surpasses all Arkansas flooding in our recorded history. That should be enough to get everyone's attention."
Just in Missouri, 52 river gauges are in major flooding, and another 40 river gauges are experiencing moderate flooding. The flooding is particularly prevalent around St. Louis and its border with Illinois.
One resident in Winfield, a city northwest of St. Louis, waded through the floodwater last Friday.
Residents in Portage Des Sioux, outside St. Louis, watched as the water rose up to their home on Tuesday.
Mississippi River gauges in Scott County, which includes Davenport, were in a major flooding zone on Wednesday.
The flooding in Iowa was so bad that a Scott County flood assistance event scheduled for Wednesday was postponed because of rising waters.
Continued rainfall and saturated ground conditions have affected the Iowa county for most of the year, according to the Scott County website. Earlier in May, several city blocks in Davenport were flooded
after the swollen Mississippi River broke through a temporary barrier and sent water into the city's downtown.