I would think you would want to possibly contact your local school paper and put something in there if you want to publicize it. Then I would imagine that you would have a dinner commemorating the event -- get some alums to come. If you are celebrating your 50th, I assume some of your founders are still alive?
Hey, in two years we will be celebrating our 135th year anniversary! Jeez, I never really thought about how long ago our chapter was founded, seems like almost 135 years ago
Brian