You are correct. Those Petticoat Junction girls were beautiful, but somehow slipped through with barely a notice. Find 2 people out of a thousand that can even remember one of their names. Same with the rest of the cast. It was a good show but just never had the drawing power to bring the same young audiance in that were watching Gilligan, F-Troop, and Get Smart.
I was just looking at some pics from that show and noticed your comment, you might like this site has sitcoms back to the 50s. I am going thru them now and WOW what memories!
http://www.sitcomsonline.com/photopost/showgallery.php/cat/504