The LEGO 4.5V train theme ran from 1966 until 1971 and contained 39 sets in all. The 4.5V trains used to be the voltage standard for the first electric LEGO components where the power came from a battery box with 3x 1.5V batteries.
1971 LEGO Sets
In 1971, LEGO expanded specifically to the girls market. While in the past LEGO marketed all of its models to both boys and girls alike, it was not until 1971 that LEGO produced furniture pieces and dollhouses for girls specifically. LEGO also continued to produce new sets for the Italian Minitalia brand as well as introduce new parts such as the 1x8x2 arch bricks which were first introduced that year.