The IBM System/360 computer series was announced in 1964. I joined the Company in 1965. The first S/370 was the IBM 145 in name only, introduced in 1972. The first real 370 was the 148 in 1973.
I worked primarily with large MVT mainframes (S/360-65 and S/360-75) until 1974 or '75 when the 370/168 grabbed a big share of the market, followed by the 3030, and later the 3090, folowed by the ES/9000.
The air went out of the sails of the water-cooled S/390 series in February 1990 when IBM introduced the RS/6000 AIX systems line. A system I could carry to my car could beat a big water-cooled mainframe with 6 Vector Facilities on a numerically intense floating point job. Today in IBM, the follow on to the RS/6000 is the pSeries p690, which borrowed and extended the ESA LPAR concept.