Project Monterey was an attempt to build a single Unix operating system that ran across a variety of 32-bit and 64-bit platforms, as well as supporting multi-processing. Announced in October 1998, several Unix vendors were involved; IBM provided POWER and PowerPC support from AIX, Santa Cruz Operation (SCO) provided IA-32 support, and Sequent added multi-processing (MP) support from their DYNIX/ptx system. Intel Corporation provided expertise and ISV development funding for porting to the new IA-64 platform, which had not yet been released at that time. The focus of the project was to create an enterprise-class UNIX for the IA-64, which at the time was expected to eventually dominate the UNIX server market.
By March 2001, however, "the explosion in popularity of Linux ... prompted IBM to quietly ditch" this;  all involved attempted to find a niche in the rapidly developing Linux market and focused their efforts elsewhere. Sequent was acquired by IBM in 1999. In 2000, SCO's UNIX business was purchased by Caldera Systems, a Linux distributor, who later renamed themselves to SCO Group. In the same year, IBM eventually declared Monterey dead. Intel, IBM, Caldera Systems, and others had also been running a parallel effort to port Linux to IA-64, Project Trillian, which delivered workable code in February 2000. In late 2000, IBM announced a major effort to support Linux.
In May 2001, the project announced the availability of a beta test version AIX-5L for the IA-64, basically meeting its original primary goal. However, Intel had missed its delivery date for the Itanium (the initial IA-64 hardware) by two years, and the Monterey software had no market.
With the exception of the IA-64 port and Dynix MP improvements, much of the Monterey effort was an attempt to standardize existing versions of Unix into a single compatible system. Such efforts had been undertaken in the past (e.g., 3DA) and had generally failed, as the companies involved were too reliant on vendor lock-in to really support a standard that would allow their customers to leave for other products. With Monterey, three of the vendors already had a niche they expected to continue to serve in the future: POWER and IA-64 for IBM, IA-32 and IA-64 for SCO.
- "Sequent "Project Monterey" Road Map". Computerworld. February 1, 1999. p. 28.
- Hughes-Rowlands and Chibib (August 31, 1999). "Project Monterey" (PDF). Project Monterey presentation. Retrieved 2007-05-20.
- "Caldera loads Linux apps on UnixWare".
- Jones, Pamela (April 25, 2005). "More Evidence Project Monterey Partners Knew Linux Was the Future". Groklaw. Retrieved 2007-05-20.
- "IBM to spend $1 billion on Linux in 2001". CNET News.com. 2000-12-12. Retrieved 2008-08-19.
- Jones, Pamela (August 25, 2005). "2002 IBM Internal Email on Project Monterey - "No One Wants It"". Groklaw. Retrieved 2007-05-20.
- Borchers, Detlef (2005-08-28). "SCO vs. Linux: 32 mal Monterey". Heise Online. Retrieved 2007-05-20.