Mississippi River floodwaters in Vicksburg, Miss., in 2011. Dave Martin/AP hide caption

itoggle caption Dave Martin/AP

Storm clouds pass over Wrigley Field on July 1, 2011, in Chicago. Jonathan Daniel/Getty Images hide caption

itoggle caption Jonathan Daniel/Getty Images

Construction on Chicago's Wells Street Bridge is taking place around the clock, as crews replace the south leaf section. The north leaf section will be replaced in the spring. The double-decked steel truss drawbridge was built in 1922. David Schaper/NPR hide caption

itoggle caption David Schaper/NPR