My wife & daughter have added enough movies to the NetFlix queue that it will be a while before I get to see Season 2. On the last Season 1 DVD, Mike & Jean graduate. Jean's parents are taking her on a last vacation for the summer. Mike & Jean are going to go to different colleges.

Then I stumbled across a thread (when searching for the Douglas' address) that said that Mike married Sally at the beginning of season 6. Having never seen seasons 1-5, I assumed that Mike married Jean in the season 6 episode (which I last saw when I was about 10).

What happened to Jean? Is she seen again after Season 1?

Jean Pearson (Cynthia Pepper) was in the Season 1 stories almost exclusively -- but she did made one final appearance, when she came back for an episode early in Season 5 (Nov. 1964). In that ep, she learns that Mike has become engaged to Sally Morrison (Meredith MacRae):

http://www.imdb.com/title/tt0655030/

Mike and Sally's wedding was in the first ep of Season 6 (Fall 1965), although their airtime in that one is pretty brief (this was the first color episode). The storyline shifts to what would eventually be Ernie's adoption. The Season 6 opener marks the only time that Tim Considine and Meredith MacRae appeared in color in the series.

The My Three Sons authority, Geoff from Australia, has provided some info at TV.com from his exhaustive files. I'll look into specifics regarding Jean when I have a chance. I've seen most of the b/w epidodes from all seasons (1-5), but not in many years.

Cynthia Pepper left after season one to star in her own sitcom, 'Margie'.

I always liked Cynthia Pepper. I actually became aware of her when she starred in the "Margie" series in 1961-62. For some reason, I missed seeing her in the role of Jean Pearson in that first season (1960-61) of My Three Sons although that show was usually on at my house.

I would like to see that November, 1964 episdoe inwhich she returns only to find that Mike is marrying Sally. Somehow - and this is admitingly because I am nostalgic - I would have liked Mike and Jean to have gotten back together in the series. In an interview made in recent years with Cynthia Pepper, she indicated that having her in that episode was Tim Considine's idea. By that time, it is understood he was becoming more interested in directing than acting. That has been said this is the reason he left the show.