National Semiconductor started selling a CPU called the Simple Cost-effective Micro Processor, or "SC/MP". This image shows the SC/MP microprocessor at the heart of a simple system and current loop to RS232 converter. Click image for larger view.

Here is a closeup of the SC/MP-1. This is the first gen version, part number ISP-8A/500. It's clocked at 1 MHz and uses P Channel MOS technology. Note the silkscreen date.
This microprocessor was first available in April 1976. Click image for larger view.