Lisp as a language might be a footnote, but the ideas the language proposed were revolutionary. Recursion, REPL and even conditionals all came from Lisp (FORTRAN had a conditional entity at the time, but not what we'd recognise as a conditional today and I believe they later adopted Lisp-style conditionals anyway). IIRC, Lisp could be expressed in 5 small base functions defined in assembly, from which the entire language could be defined in turn, making it outrageously portable.

It's hard to understate how seminal Lisp was.