My Gr-Grandfather is listed as Lake Captain in the 1890 Chicago City Directory. From various "soft" sources I've gotten names of possible ships: the A G Mowry and the Juno are just 2. I've also heard that he contracted for Morton Salt, although their historian reports not having any of these kinds of records.
His name was Sakarias Berntson, or Zacharias Benson as it was Americanized. There are many possible spellings, as you can imagine.
Does he appear anywhere in your database?