Co-founded by hard drive pioneer Alan Shugart and partners, Seagate Technology was originally incorporated as Shugart Technology in November 1978 and began operations the following year, which largely included efforts to create a 5.25-inch HDD after foreseeing a boom in the market.
The company's name was changed to Seagate in 1979 to avoid a lawsuit from a similarly named Xerox subsidiary, Shugart Associates, a computer peripheral manufacturer founded by Shugart in 1973 that is perhaps best known for introducing the 5.25-inch minifloppy floppy disk drive.
Shugart/Seagate was first to market with a 5.25-inch hard drive, the micro-Winchester ST-506, which offered a capacity of 5MB and was first purchased by Digital Equipment Corporation (DEC -- acquired by Compaq in 1998).
Storage Technology Corporation was founded in 1969, focused on backup storage technology and was purchased by Sun Microsystems for $4.1 billion in 2005. Maxtor was a rival HDD maker founded in 1982 and acquired by Seagate in 2006. Western Digital, as a random aside, was founded in 1970 as "General Digital," a maker of MOS test gear.