Oh boy, there was William Williams, right age, immigrant from England, working in a mine in southwest Idaho on the 1900 census. But having chased Bill from England to Michigan then to South Dakota and eventually to Wardner, Idaho, how could I be sure this was the right one?
The picture below was among family photos passed down to Ken Williams, a great grandson of Bill. In fact there were two copies of the photo, a pretty good indication that there was a family member in it.
Will the real Bill Williams please stand up? That is, if the real Bill Williams is in this picture. We'll probably never know which man is Bill but there is enough circumstantial evidence to place him in Owyhee County in 1900. The clue--the photographer. C. E. Joy had a photograph studio in Salt Lake City around 1900 and probably made trips to neighboring communities.
Looking for the clues
There are many clues for dating and identifying photos. Prominent among those is researching the photographer.
The ten second Google search--a quick search on the name and city may hit paydirt.
A single named photographer, "Joe Blow" might be in the census with his photographer occupation.
Check histories of the town or county--the pictures below were taken by Burnham & Boynton, Spokane Falls, Wash. Ter. Family history is that the couple migrated to Post Falls, Idaho Territory about 1886.
Check city directories and newspapers. By 1890, Oscar Boynton was in the Spokane City Directory as a photographer working for E E Bertrand. Partners may separate for some reason. Studios may not use a person's name.
U. S. City Directories, 1822-1995 Ancestry.
If there are several photos, taken by numerous photographers, setting up a table or spreadsheet may be helpful in dating and identifying. Placement of photographer Adam Heeb helped identify Susannah and also the bride and groom.
A prominent photographer may move from one location to another and the address on the photo imprint will help to nail down dates.
It was difficult to identify the boy in the photo because none of this family had ever lived in or near Fargo, Dak. And yet the clue was right there, "visits all cities on the Northern Pacific Railroad" with the picture of his Palace Studio Car.
Newspapers would carry this ad for several weeks prior to the scheduled stop and the several Haynes photos in the family collection can be dated by the address on the mat.
When we get back to walking into libraries, Bellevue Branch of KCLS has several good books in the Reference Section, among them:
Carl Mautz, Biographies of Western Photographers, Carl Mautz Publishing (Bellevue Public Library, Reference Section)
Try these clues and you'll probably find some clues of your own. Happy hunting!