An old photograph

There is a stack of old family photographs that my mother gave me a few years ago. Some of them date to the early 20th century, some are even earlier. I must admit I know very little about the people in these pictures. One is especially vexing:

Who are these people? What was the occasion? Is this my immediate family? Probably not, but still I am curious as to why the picture is in my posession. I should probably have an "interview" with my mom and make a good description of every photograph in a digital format. Can't let these memorabilia perish.