Minnesota was officially shut off from the outside world Tuesday -- for lake and ocean shipping, anyway -- when the locks at Lake Superior's southeastern tip were closed for annual maintenance. 


 The 767-foot Cason J. Callaway (above), loaded with 25,000 tons of taconite pellets loaded at Two Harbors, Minn.,, passed through the Poe lock at Sault Ste. Marie, Mich. just after sundown Tuesday.  It was headed for Indiana Harbor at the southern tip of Lake Michigan, south of Chicago, to deliver the iron ore, and then to Sturgeon Bay, Wis., where it will spend the winter. . 

The Soo Locks, as they are known, are scheduled to close every year on Jan. 15 for winter maintenance, regardless of weather conditions, unless shippers ask for an extension of the season. They're scheduled to re-open March 25. 

 During the 2012 navigation season, 4,086 cargo vessels passed through the Soo Locks carrying about 75 million tons of iron ore, coal, grain and other commodities. Another 3,278 tour boats, private boats and other recreational vessels used the locks this past year.