1964: IBM Introduced the System/360
It was the first family of computers designed to cover the complete range of applications, from small to large, both commercial and scientific. The design made a clear distinction between architecture and implementation, allowing IBM to release a suite of compatible designs at different prices.
See the IBM Press Release via the link below.
Photo is of the IBM System/360 Model 30 at the Computer History Museum. Photo info: "IBM System360 Model 30" by Dave Ross - Flickr: IBM System/360 Model 30. Licensed under CC BY 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:IBM_System360_Model_30.jpg#/media/File:IBM_System360_Model_30.jpg