Many archives are now working to digitize collections of their photos to make access easier for researchers to do preliminary research from their home or office, and to minimize the handling of originals.
To track down digital images, start your research in the appropriate archive for your location or subject (municipal/provincial/federal OR cultural/industrial/artistic), and see if they have a photo database you can search.
Every database will be slightly different but generally, you can enter date parameters, location, and photographer information, plus a subject you think will be appropriate to carry out your search.
But not all of these databases are user-friendly so write or phone the archives and ask for step-by-step instuctions or help in using them.
Don’t feel embarrassed or shy about asking for help.
Archivists know that their databases can be challenging to use and are usually more than willing to help you navigate and find something you’re looking for.
They want you to succeed!
Bear in mind that the images you see may only be in a thumb-nail version, or they may be bigger, but regardless, your use of them will generally be limited to research purposes only unless and until you’ve made arrangements with the archives that holds the copyright to that photo.
Considerations of fair use, copyright, and costs for various kinds of use including replication in books or used for a commercial purpose such as a poster, t-shirt, mug, or marketing material.