I pulled this from the Aperture Science website before when you could've logged in... this pretty gives a detailed history of Aperture Science and some details of Portal 2.
1953 - Aperture Science begins operations as a manufacturer of shower curtains. Early product line provides a very low-tech portal between the inside and outside of your shower. Very little science is actually involved. The name is chosen to make the curtains appear more hygienic.
1956 - Eisenhower administration awards Aperture a contract to provide shower curtains to all branches of the military except the navy.
1957-1975 - Mostly shower curtains.
1978 - Aperture Founder and CEO, Cave Johnson, is exposed to mercury while secretly developing a dangerous mercury-injected rubber sheeting from which he plans to manufacture seven deadly shower curtains to be given as gifts to each member of the House Naval Appropriations committee.
1979 - Both of Cave Johnson's kidneys fail. Brain damaged, dying, and incapable of being convinced that time is not now flowing backwards, Johnson lays out a three tiered R&D program. The results, he says, will 'guarantee the continued success of Aperture Science far into the fast-approaching distant past.'
Tier 1: The Heimlich Counter-Maneuver - A reliable technique for interrupting the life-saving Heimlich Maneuver.
Tier 2: The Take-A-Wish Foundation - A charitable organization that will purchase wishes from the parents of terminally ill children and redistribute them to wish-deprived but otherwise health adults.
Tier 3: 'Some kind of rip in the fabric of space... That would... Well, it'd be like, I don't know, something that would help with the shower curtains I guess. I haven't worked this idea out as much as the wish-taking one.'
1981 - Diligent Aperture engineers complete the Heimlich Counter-Maneuver and Take-A-Wish Foundation initiatives. The company announces products related to the research in a lavish, televised ceremony. These products become immediately wildly unpopular. After a string of very public choking and despondent sick child disasters, senior company officials are summoned before a Senate investigative committee. During these proceedings, an engineer mentions that some progress has been made on Tier 3, the 'man-sized ad hoc quantum tunnel through physical space with possible applications as a shower curtain.' The committee is quickly permanently recessed, and Aperture is granted an open-ended contract to secretly continue research on the 'Portal' and Heimlich Counter-Maneuver projects.
1981-1985 - Work progresses on the 'Portal project. Several high ranking Fatah personnel choke to death on lamb chunks despite the intervention of their bodyguards.
1986 - Word reaches Aperture management that another defense contractor called Black Mesa is working on a similar portal technology. In response to this news, Aperture begins developing the Genetic Lifeform and Disk Operating System (GLaDOS), an artificially intelligent research assistant and disk operating system.
1996 - After a decade spent bringing the disk operating parts of GLaDOS to a state of more or less basic functionality, work begins on the Genetic Lifeform component.
Several Years Later - The untested AI is activated for the first time as one of the planned activities on Aperture's first annual bring-your-daughter-to-work day.
In many ways, the initial test goes well...
Oh yeah, THIS IS SPARTA
Apparently, Portal 1 takes place sometime in 2010, which means it is taking place either before or around the time of Half Life 2, as Half Life 1 took place in 'present day' which was 1996 in that case, and Gordon Freeman woke up from a 20 year stasis in Half Life 2. Portal 2 takes place several hundred years after Portal 1, which means centuries after Gordon Freeman and the HL2 Characters have died.