PACIFIC, Mo. — The floodwaters that swept away cars and swamped living rooms decorated for Christmas slowly drained from homes and businesses outside St. Louis on Friday, leaving behind months of cleanup as the threat of record-breaking floods headed south toward towns and farm communities flanking the Mississippi River.

As people in southern Missouri and Illinois evacuated their homes or moved furniture to the second floor, nervously eyeing the river rising along flood walls, highways that flooded around St. Louis were reopened on Friday, and some soaked communities began allowing residents to return to survey the damage.

In Pacific, one of several hard-hit towns southwest of St. Louis, about 20 people lined up at a police checkpoint on Friday morning, home-inspection papers in hand, anxiously waiting to learn whether they would be allowed back in to see what was left. They were among hundreds who fled when the rain-engorged Meramec River spilled across highways and through neighborhoods, shattering flood records and rising to 27 feet above flood stage in some places.

Mitchell Duncan, 25, kept cycling through the line as the police told him he could not return to his rented duplex because it had yet to be inspected. He said he was impatient — he had left six days earlier without taking anything because he did not think the floods would be so bad.