Cities along the Mississippi River are sandbagging and evacuating downtown homes and businesses as floodwaters that overwhelmed defenses in Davenport, Iowa, earlier in the week make their way toward St. Louis. Flood gauges near Davenport, where the river has been at major flood stage for 42 days, broke a record level set in 1993 before cresting Thursday. A temporary flood barrier gave way Tuesday, flooding a two-block area of downtown. …