Six people died on slick roadways yesterday as a killer ice storm gripped heartland America, turning sidewalks and highways into ice rinks, grounding flights and downing power lines. The storm turned a swath of the nation frigid from the Southern Plains to the Great Lakes, and even colder weather threatened today.
                                    
                                    
                                
                                
                             
                            
                            
                            
                            
                            
                                
                                
                                    
                                        Some communities reported ice as thick as three-quarters of an inch in Missouri, where the governor declared a state of emergency and called out the National Guard. Chicago's O'Hare International Airport canceled more than 400 flights. The  frigid weather was expected to continue until mid-week with ice storm warnings reaching from Pennsylvania to Texas.