Hi Becky -
The crew information comes from a database I have been developing over the past several years. I have compiled crew information from over 1000 reference sources including Great Lakes Red Books, shipping company newsletters, trade magazines, newspaper accounts, books, LCA crew lists, fleet seniority lists, Internet searches, and personal contact with current and former sailors. The information is in a simplified spreadsheet format that I can readily search based on the last name of an individual or the name of a boat. Currently, the database has something like 265,000 entries that span the time frame 1850 - 2008.
It is "easiest" to find information on sailors that achieved the rank of Captain or Chief Engineer. It becomes increasingly more difficult if an individual sailed at a lower rank, sailed for a short period of time, or sailed a long time ago.