Originating in 1960, Lisp is second only to Fortran as the oldest programming language still in use today. Historically used for research, artificial intelligence, and mathematics, Lisp remains relevant in these fields, as well as in quantum computing research and other cutting-edge applications. In the mid-1970s, researchers sought high-performance, single-user, interactive machines due to the constraints of running their code on large multi-user mainframes. Such machines would allow for more efficient and flexible research and development. Richard Greenblatt at the MIT AI Lab spearheaded the development of the first dedicated Lisp machines, including the successful CONS machine and later CADR machines. MACSYMA, a symbolic mathematics program written in Lisp which consumed significant resources on the PDP-10 running ITS, was a key motivator for the Lisp Machine's creation. LispM hackers in residence, including Daniel Weinreb (DLW), David Moon (MOON), Richard Stallman (RMS), John L. Kulp (JLK), Mike McMahon (MMcM), and others, were responsible for the overall system development. Kulp designed the legendary Space Cadet keyboard, known for its unique key arrangements and symbols, and Moon and Weinreb wrote the first and second Lisp Machine editors (EINE, ZWEI) respectively. Brad Parker developed the first working CADR simulator (usim), which emulates the MIT CADR, and with the Lisp Machine microcode running on top, allows users to explore the historic system and its unique features. Until recently, only up until system 78 of the LISP operating system and microcode from MIT could be emulated. Alfred M. Szmidt (AMS) received copies of backup tapes containing systems 98 and 99, dating from 1983 and 1984, respectively, and was able to get them running after a decade of effort. The bootstrap process was an impressive hack, due to the Lisp Machine's use of network booting and a mixture of compiled and uncompiled code. Szmidt has now iterated the distribution to system 100 with all of his fixes included. This marks the first time in 35 years that anyone can use this environment, designed to support AI and computational research at the cutting edge. The windowing and graphical feel of the environment stand out, and the Lisp machine and CADR processor allow users to dive deep into the operating system's inner workings. The line between compiled and source code is thin, and users can open and read almost everything. The CADR machine served as the foundation for commercial products sold by LISP Machines, Inc., founded by Richard Greenblatt, and Symbolics, founded by MIT AI Lab ex-administrator Russell Noftsker. The emulator provides a glimpse into the height of 80s MIT hacker culture by booting to MIT System 100. Find more information and try the system out yourself via AMS's announcement post: https://tumbleweed.nu/r/bug-lispm/forumpost/7475d8a3db Or visit https://tumbleweed.nu/lm-3 -Eric