Directories are great sources, but don’t neglect to see if there are lists in the back of individuals with various businesses and occupations. This 1891-1892 directory of Rock Island, Illinois, contained a reference to a boarding house owned by Mrs. Louisa Mortier. That was a discovery and now I need to see if the address of the boarding house is the same address listed as her husband’s reference. The family had no boarders listed in their 1880 census enumeration–but that was almost ten years before the reference in this city directory.
A relative may easily have had a business or occupation of which you were unaware.