Thank you! I think you are right because the only thing I had to go on was the roof line. I found this picture which shows the passenger side that seems to be a match. The little door to the left of the girl on the running board (gas cap?) even matches. I found an ad for a 1920 Marmon for $3350, which is like $45,000 today, and that seems to be in the right price range for a well-to-do kid who graduated high school in 1921.
Again, thank you so much.