In 1927, the Minneapolis Honeywell Regulator Company was formed as a merger of Alfred Butz' temperature control company (1885) and Mark Honeywell's water heater company (1906). In 1957, Honeywell, along with Ratheon, introduced one of the first computers in the U.S., the Datamatic 1000. Two years later, Honeywell's 800 and 400 models earned a solid reputation for advanced features.

In the mid-1960s, Honeywell's 200 series gave IBM serious competition. It outperformed IBM's very successful 1401 computer, which it emulated, causing IBM to accelerate its introduction of its System/360. In 1966, Honeywell acquired Computer Control Company's minicomputer line, and in 1970, it acquired the assets of GE's computer business. The computer division was renamed Honeywell Information Systems, Inc.

Through Honeywell's association with Groupe Bull in Europe and Bull's association with NEC in Japan, research and development were mutually explored and products were jointly developed. In the late 1980s, the three companies formed Honeywell Bull, and later Bull acquired the majority interest, renaming the organization Bull HN. The famous Honeywell name, having been identified with the most advanced computers, remained only as the "H" in Bull HN.