Comment by gjm11

Visicalc: 1979. Excel: 1985. Garnet: early 1990s. Cells: 2000 or so.

On the other hand ... Sketchpad: 1963. (Constraint satisfaction, but not embedded in a general-purpose programming system.) Prolog: 1972. And Guy L Steele wrote a nice general-purpose constraint system in 1978. ("Constraints", MIT AI Memo 502.)