I have to say the 1957 catalogue because that is the year that Santa brought me my first Lionel trains set which appeared in that catalogue. It was a freight set with 3 operating cars ( milk, Pacemaker boxcar, and log dump car ) , a three dome Sunoco tank car, and lighted Lionel Lines caboose, all pulled by a 2065 hudson steam locomotive. I still have that set and it still operates until this day.
I loved all the catalogues from 1956 on. I used to sit looking through those catalogues and let my imagination run wild. Those catalogues were some major fuel for the imagination!!!