History of Half-Life Science

The Combine Overwiki has full articles on Aperture Science and Black Mesa. These articles cover all that is canonically known about these organizations. A quick summary:

Aperture Science

• Location: Upper Michigan
• Purpose: Originally created as a shower curtain manufacturer by a successful shower curtain salesman, the company eventually evolved "into an experimental physics research institution and a bitter rival of Black Mesa" after the owner became deathly ill and brain-damaged.

Black Mesa

• Location: A city called "Black Mesa" in New Mexico
• Purpose: Helmed by the U.S. Government, Black Mesa conducts research in various theoretical and applied science fields.

Valve had a "GLaDOS Terminal" set up at www.aperturescience.com for a long time. With the right logon and commands you could see a compressed history of Aperture Science. It appears to be gone now (replaced by a Christmas video) but you can still access it here. Type login, Use the username cjohnson and the password tier3 to log in, then issue the notes command.