A major pre-CommonLisp implementation of Lisp at MIT.  MacLisp had DynamicScoping implemented with ShallowBinding.

MacLisp was used for a great many amazing things, including the bootstrapping of the SchemeLanguage (which was compiled to MacLisp.) Its name derives from the MAC Project at MIT, and ''not'' from the AppleMacintosh computer series (which it predated by almost two decades).

The MacLisp reference manual (aka Moonual, after its author, DavidMoon) can be found in the ''lspman'' directory from the ''AI'' machine's filesystem at http://www.its.os.org/. There are a lot of other historically significant things on this filesystem, including the TecoEditor source to the original EmacsEditor.

''There is no ''lspman'' directory on ''AI'' as of 26dec2003. Other links?''
* The its.os.org maintainer tells me that the missing manual was not the 1974 "Moonual", but rather a 1983 version copyright KentPitman, who requested that it not be redistributed there -- nor apparently is he making it otherwise available as of 2005-Jul-16. But he has indicated that if and when he makes it available, it will be in the same spot as the rest of his publications: http://www.nhplace.com/kent/Papers/index.html (lots of good reading there).

See also a version of the MacLisp manual at
http://pdp-10.trailing-edge.com/mit_emacs_170_teco_1220/01/info/lisp.info.html (warning, large page, that's the entire manual in one html page)

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How related is MacLisp to Emacs Lisp? 

''The relationship between MacLisp to Emacs Lisp is indirect: the author of Emacs and Emacs Lisp, Richard Stallman, developed Emacs at MIT and was associated (in some sense) with MitProjectMac, but Emacs Lisp itself is a rewrite from scratch, as is the current Emacs (the original Emacs was written in the Teco language). Almost all Lisps have been indirectly influenced by MacLisp, which in turn was influenced by the original LispOnePointFive.''

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The MacLisp compiler also has been optimized to support fast numerical processing.