As Lee stated, Lionel prewar is from 1900 to 1942. Postwar was from 1945 to 1969. Both eras, same company as founded by Joshua Cowan.
Even though the first 15 years of the modern era tends to be called the "MPC era," 1970-1972 is the actual "MPC era" as this was the time period that Lionel trains was organized as a toy division under MPC. I tend to regard those years as the General Mills era as it's more accurate.
Lionel train production was reorganized in 1973 and fell under a new division called "Fundimensions" and no longer was under MPC. It would essentially remain this way up until 1985 when Lionel was very briefly spun off under Kenner-Parker, which was also spun off from General Mills prior to Richard Kughn purchasing Lionel from Kenner Parker.
1986 to 1995 was the "Richard Kughn" era, where he formed Lionel Trains, Inc. (LTI) until he sold off his majority share to Wellsprings, where the company was reformed as Lionel LLC which remains today, although majority ownership transferred from Wellsprings to Guggenheim in the early 2000s during the Lionel-MTH lawsuit.
Contrary to what some causal observers think, Lionel (as in the company) was "not bought out" by MPC/General Mills. The Lionel Corporation sold their toy train line (including American Flyer) which also involved the tooling, to General Mills, and licensed the Lionel name for them to use, so in essence the direct lineage of Lionel trains to the company was severed, so there's no direct connection between The Lionel Corporation and what is now Lionel LLC today.
Lionel Corporation continued on as a holding company that invested in other companies, including electronics, camping gear, and retail toy stores (Lionel Toy City, Lionel Kiddie & Lionel Leisure), continuing to receive royalties from General Mills (later LTI) until they finally sold the Lionel name & trademarks to LTI before finally going insolvent and out of business in 1993.
