The Cason J. Callaway Appears Next

The next ship appeared fairly quickly.

 I think the Callaway was in the locks when the Saginaw appeared.  That meant she was about a half hour away from Mission Point.

 I was happy to catch her because she is one of the last AAA freighters left.

 I think she was on her way to Conneaut.

Which likely means she was carrying taconite.