Morris’s mother was the former Alice Edna Swaim. His father, George Washington Jessup, was a farmer. Around 1902 Morris’s only sibling, Marjorie, was born.

Born near Rockville, Indiana, Jessup grew up with an interest in astronomy. He earned a bachelor of science degree in astronomy from The University of Michigan in Ann Arbor, Michigan in 1925 and, while working at the Lamont-Hussey Observatory, received a master of science degree in 1926. Though he began work on his doctorate in astrophysics, he ended his dissertation work in 1931 and never earned the higher degree. Nevertheless, he was sometimes referred to as "Dr. Jessup." Jessup has been referred to in ufological circles as "probably the most original extraterrestrial hypothesiser of the 1950s". Some sources refer to him as an instructor in astronomy and mathematics at the University of Michigan and Drake University. Jessup achieved some notoriety with his 1955 book The Case for the UFO, in which he argued that unidentified flying objects (UFOs) represented a mysterious subject worthy of further study. Jessup speculated that UFOs were "exploratory craft of "solid" and "nebulous" character." Jessup also "linked ancient monuments with prehistoric superscience. Jessup wrote three further flying-saucer books, UFOs and the Bible, The UFO Annual (both 1956), and The Expanding Case for the UFO (1957). The latter suggested that transient lunar phenomenon were somehow related to UFOs in the earth's skies. In Florida, he was involved in a serious car accident and was slow to recover. In 1958 his wife left him, and his friends described him as being somewhat unstable when he traveled to New York City. On April 19, 1959, Jessup contacted Manson Valentine and arranged to meet with him the next day, claiming to have made a breakthrough regarding an event known as the Philadelphia Experiment. However, on April 20, 1959, Jessup was found dead in Dade County, Florida, with a hose between the exhaust pipe and a rear window of the vehicle, filling the car with toxic exhaust fumes. The death was ruled a suicide. Some people believed that "The circumstances of Jessup's apparent suicide remain mysterious" and conspiracy theorists contended that it was connected to his knowledge of the "Philadelphia Experiment". Although some friends claimed that he possibly had been driven to suicide by the "Allende Case," other friends said that an extremely depressed Jessup had been discussing suicide with his friends for several months before committing suicide.

Books by Jessup
Jessup, Morris K. (1955). The Case for the UFO. New York: Citadel Press.
Jessup, Morris K. (1956). UFOs and the Bible. New York: Citadel Press.
Jessup, Morris K. (1956). The UFO Annual. New York: Citadel Press.
Jessup, Morris K. (1957). The Expanding Case for the UFO. New York: Citadel Press.

Morris’s mother was the former Alice Edna Swaim. His father, George Washington Jessup, was a farmer. Around 1902 Morris’s only sibling, Marjorie, was born.

Born near Rockville, Indiana, Jessup grew up with an interest in astronomy. He earned a bachelor of science degree in astronomy from The University of Michigan in Ann Arbor, Michigan in 1925 and, while working at the Lamont-Hussey Observatory, received a master of science degree in 1926. Though he began work on his doctorate in astrophysics, he ended his dissertation work in 1931 and never earned the higher degree. Nevertheless, he was sometimes referred to as "Dr. Jessup." Jessup has been referred to in ufological circles as "probably the most original extraterrestrial hypothesiser of the 1950s". Some sources refer to him as an instructor in astronomy and mathematics at the University of Michigan and Drake University. Jessup achieved some notoriety with his 1955 book The Case for the UFO, in which he argued that unidentified flying objects (UFOs) represented a mysterious subject worthy of further study. Jessup speculated that UFOs were "exploratory craft of "solid" and "nebulous" character." Jessup also "linked ancient monuments with prehistoric superscience. Jessup wrote three further flying-saucer books, UFOs and the Bible, The UFO Annual (both 1956), and The Expanding Case for the UFO (1957). The latter suggested that transient lunar phenomenon were somehow related to UFOs in the earth's skies. In Florida, he was involved in a serious car accident and was slow to recover. In 1958 his wife left him, and his friends described him as being somewhat unstable when he traveled to New York City. On April 19, 1959, Jessup contacted Manson Valentine and arranged to meet with him the next day, claiming to have made a breakthrough regarding an event known as the Philadelphia Experiment. However, on April 20, 1959, Jessup was found dead in Dade County, Florida, with a hose between the exhaust pipe and a rear window of the vehicle, filling the car with toxic exhaust fumes. The death was ruled a suicide. Some people believed that "The circumstances of Jessup's apparent suicide remain mysterious" and conspiracy theorists contended that it was connected to his knowledge of the "Philadelphia Experiment". Although some friends claimed that he possibly had been driven to suicide by the "Allende Case," other friends said that an extremely depressed Jessup had been discussing suicide with his friends for several months before committing suicide.

Books by Jessup
Jessup, Morris K. (1955). The Case for the UFO. New York: Citadel Press.
Jessup, Morris K. (1956). UFOs and the Bible. New York: Citadel Press.
Jessup, Morris K. (1956). The UFO Annual. New York: Citadel Press.
Jessup, Morris K. (1957). The Expanding Case for the UFO. New York: Citadel Press.