Neatorama reader Steven Stengel has a neat collection of old, ... er vintage computers from the 70s and 80s.
This one to the left is IBM 5100, which is considered the world's first portable computer.
The Model 5100 is IBM's first microcomputer, i.e. not a mainframe, and is also considered the world's first portable computer. Although at 55-pounds, it might best be described as "self-contained" rather than "portable".
There were very few other computers available at the time, and nothing even close to the capabilities of the 5100. It is a very complete system - with a built-in monitor, keyboard, and data storage. It was also very expensive - up to US$20,000. It was specifically designed for professional and scientific problem-solvers, not business users or hobbyists.
Link - Thanks Steven!