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
In 1972, The LEGO Group officially expanded into the United States, marking a major milestone in the company's global growth. Following a licensing dispute with the Samsonite Corporation, LEGO USA was established in Brookfield, Connecticut. As a result, Samsonite ceased production of LEGO products in the U.S. but continued manufacturing and distributing LEGO sets in Canada until 1986. This transition allowed LEGO to take full control of its branding, marketing, and distribution in the American market.