They are very common in Quebec. You can find them in each entrance of
each small village (often 2 of them).
Most villages are catholic. and those memorials are often related to a
saint (which patronages the village, and often after whom the village is
named). You will find few symbols such as a ladder (climb to paradise?),
tools or icons.

Each one is symbolic, has a meaning regarding the community and the
village (farmers vs fishermen, etc.)
Lots of different combinations. Almost identifying the village.
I know of a guy named Carpentier, an historian related to the Museum of
Civilizations in Ottawa/Hull that did his thesis and a book on this 30
years ago. (he might be retired now).

There is the same in France (in Brittany at least, but in stone, they
are often named Pardon, Calvaire, or Cross of...). They also helped for
directions while travelling.

here in Quebec, there are called Croix de chemin.
english:
http://www.patrimoine-religieux.qc.ca/croix/croixe.htm
in French: I hope google's translation is meaningfull.
http://www.borealie.org/page.php/fr/1/94.html
http://www.mcc.gouv.qc.ca/publications/collpat/endos/d90.htm
http://www.patrimoine-religieux.qc.ca/croix/croix1f.htm
http://pages.infinit.net/mipic/texts13-4.htm

JP