HKEPC have posted up a detailed timeline of Intel's microprocessor path dating back to 1971 - Quite an interesting read if you'd like to learn about the company's history of processor families.
The 4004 was Intel's first microprocessor. Intel began development of the first microprocessor in 1969 as part of a project for Japanese calculator manufacturer Busicom to develop a set of chips for a family of programmable calculators. This breakthrough invention powered the Busicom calculator and paved the way for embedding intelligence in inanimate objects as well as the personal computer.
Originally, Busicom owned the rights to the microprocessor having paid Intel $60,000. Realizing the potential for the "brain" chip, Intel offered to return the $60,000 in exchange for the rights to the microprocessor design. Busicom agreed and Intel introduced the 4004 (right) to the worldwide market on November 15, 1971. The 4004 sold for $200 each. The 4004 processors contain 2,300 transistors.