Officially announced in U&lc Vol. 1 No. 3 (1974), but already mentioned in Vol. 1 No. 1 (1973) as ITC’s “newest text type”.
“… strikes a happy compromise with its forerunner. The rigid spacing is dispensed with, but the distinctive typewriter flavour is generously enhanced. And there is just enough nostalgia in American Typewriter to give it a top billing in contemporary typography.” [1975 specimen] The forerunner appears to be Typewriter 4 as shown in PLINC’s One Line (1971), listed in the index with alias American Typewriter.
The two lighter weights were designed by Joel Kalden and the Bold (plus Outline) by Tony Stan.