Gregg is the youngest child of Robert and Margaret Gregg. They move to Rockcorry in 1872. Robert Gregg, who is of Scottish ancestry, is station-master at the Bushford railway station in Rockcorry. He and his wife raise their children as strict Presbyterians, and send their children to the village school in Rockcorry. On Gregg’s second day of class, he is caught whispering to a schoolmate, which prompts the schoolmaster to hit the two children’s heads together. This incident profoundly damages Gregg’s hearing for the rest of his life, rendering him unable to participate fully in school, unable to understand his teacher. This ultimately leads to him unnecessarily being perceived as dull or mentally challenged by his peers, teachers, and family.
In 1877, one of Robert Gregg’s friends, a journalist named Annesley, visits the village for a weekend. He is versed in Pitman Shorthand and takes verbatim notes of the sermon at the village church. This causes the preacher to sweat and stutter out of fear that his sermon, which he has plagiarized from a famous preacher, would be made public through Annesley’s notes. That day, Robert Gregg sees the shorthand skill as a powerful asset, so he makes it mandatory for his children to learn Pitman shorthand, with the exception of John, who is considered by his family too “simple” to learn it. None of the children succeed in fully learning the system. On his own, John Robert learns a different shorthand system, that of Samuel Taylor, published in a small book by Odell. He teaches himself the system fully since he does not require the ability to hear in order to learn from the book.
Due to hardships on the family, Gregg has to leave school before the age of 13 in order to support his family’s income. He works in a law office, earning five shillings a week.
Gregg professes he initially set out to improve the English adaptation by John Matthew Sloan of the French Prévost Duployan shorthand, while working with one of Sloan’s sales agents, Thomas Malone. Malone publishes a system called Script Phonography, of which Gregg asserts a share in authorship is owed to him. Angered by Malone, Gregg resigns from working with him and, encouraged by his older brother Samuel, publishes and copyrights his own system of shorthand in 1888. It is put forth in a brochure entitled Light-Line Phonography: The Phonetic Handwriting which he publishes in Liverpool, England.
In 1893, he emigrates to the United States, where he publishes in the same year Gregg Shorthand. The method meets with great success in the new country, and Gregg settles in Chicago where he authors numerous books for the Gregg Publishing Company on the subjects of shorthand and contemporary business practices.
John Robert Gregg dies in New York City, at the age of 80, on February 23, 1948.