In 1972 LEGO released the 4.5V and 12V train sets as part of the Blue Era which was named because of the rail color. These train sets used additional conductor rails mounted between the standard 4.5V rails and 12V motors contained in the same housings as the 4.5V motors, but with additional metal contacts attached to the bottom of the housings.
1972 LEGO Sets
1972 was a pivotal year in LEGO’s U.S. expansion. Following the end of its Samsonite license, LEGO founded LEGO USA in Brookfield, Connecticut, while Samsonite continued production in Canada. The year also brought key new parts—including the first boat hulls, wings, propellers, and helicopter rotors—broadening creative possibilities. Trains remained a major focus with sets such as 181 Train Set with Motor, 180 4.5V Train with 5 Wagons, and 724 12V Diesel Locomotive, continuing to enhance LEGO’s realism and play depth.