How Did The Gulfstream I Develop?

The Grumman Gulfstream I, or G-159, was a twin turboprop business jet that first flew on August 14, 1958. Grumman Aircraft Engineering Corporation saw that there was a demand for a business jet that was comfortable and efficient and would suit the business aviation market. They also considered that it could be used as a regional airliner. Two hundred of the aircraft were built between 1959 and 1969, but how did the Gulfstream I develop?