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.
1967 LEGO Sets
In 1967, LEGO standardized its model scale, moving from the 1:87 Town Plan format to the larger 2×2 wheel scale used in Train and Model Maker sets. This unification set the stage for the modern LEGO System and the eventual minifigure scale of the late 1970s. New innovations included black rubber tires, the first hinge elements, and LEGO’s earliest promotional tie-ins—six exclusive sets released through Kraft Velveeta. The phasing out of Town Plan and 1:87 vehicles marked the end of LEGO’s early era and the beginning of a consistent global design standard.