The river's high water has closed only the President Casino and a handful of other businesses along the city's riverfront.
Upriver from St. Louis, the river is slowly receding in hard-hit towns like Winfield and Foley, Missouri, but it will be some time before residents can assess the damage.
"It was a valiant effort," said Chris Azar of the Winfield-Foley Fire Department after a makeshift sandbag levee gave out early Saturday morning. "It's unfortunate that we couldn't do more but Mother Nature won. Now, just give it time for the water to recede."
Evacuees are mostly staying with relatives or friends, though a few were staying at a Red Cross shelter set up at the high school.
Winfield, 45 miles northwest of St. Louis, is in Lincoln County, which has been particularly hard hit by flooding caused by torrential rain that fell across the Midwest in early June.
While Winfield lost the battle to save its levee, some Missouri towns have apparently weathered the threat.
The levee held at Alexandria, a tiny town near the Iowa state line, and water is receding, allowing evacuees to move back home. A few houses had water inside, but nothing irreparable.
A massive sandbagging effort was still protecting most of the businesses in Clarksville, and water was still high but receding in nearby Louisiana. Both of those towns don't have levees.
Downriver from St. Louis, the river is expected to crest Wednesday at Cape Girardeau at just over 12 feet above flood stage. Thousands of acres of farmland are flooded but a floodwall protects Cape Girardeau and most of its 36,000 residents.