Yes, massively influential, but was it ever used or popular?, I always think of it as sort of the poster child for the danger of "design by committee".

Sure it's ideas spawned many of today's languages, But wasn't that because at the time nobody could afford to actually implement the spec. So we ended up with a ton of "algols buts" (like algol but can actually be implemented and runs on real hardware).

Used extensively on Burroughs mainframes.