Harmon Jessie Platt was born March 10, 1891, near Waverly, Kansas, the second child of C. C. and Annie Platt. His nickname was H. J. and he was called that about half the time.
With C C in the Ford business, Harmon sold out his interests in Drumright and came to Stillwater to learn the Ford business. When he had absorbed what he needed he established a Ford agency at Perkins and being successful there he sold out and moved to Claremore, where he did an immense business, having the best Ford business in the state. He later sold it and moved to Oklahoma City to rest up for a while. (This paragraph taken from the Maramec Paper, 1919.)
While in Claremore he became friends with Will Rogers.
H. J. built the world's first Recreational Vehicle, a motor home that he called the "Home DeLux", on a Ford truck chassis and used for camping trips. The home was quite a novelty and on July 17, 1919, successfully climbed the world's highest motor drive - the summit of Pike's Peak . This attracted the attention of thousands and its photograph appeared in many newpapers across the United States. It was equipped with a bed with springs, a two-burner gas stove with oven, table, cupboard with five shelves, 50# ice box, 16 gallon water tank, clothes box and two long box seats on each side containing the bedding. It was also equipped with electric lights, toilet, linoleum floor covering, Japanese window shades and was screened with copper wire. Total cost of the vehicle was $2490.
Harmon and his brother Raymond purchased the French & Son Ford Garage in Perkins, and quickly built up the business. Harmon was the business manager and Raymond was the expert mechanic. In November 1919, the Platt Brothers began construction of a new brick garage at 219 S. Main Street, now Perkins Food Center. The new building was 45 feet by 120 feet and was one of the finest garages in the area. In February 1920, Harmon purchased Raymond's interest in the business and Raymond took a salaried position in the workshop. The opening of the new garage took place May 1, 1920. The Ladies Aid Society of Perkins served ice cream, there was music, and from 9:00 p.m. until 11:30 p.m. social dancing was held, however, "no execrable forms of dancing" were allowed and strict decorum enforced. )

In all, the Platt brothers had invested nearly $27,000 in Perkins. The stock room contained over $8000 worth of parts and accessories that were all organized in sections allowing the office man to locate the parts quickly. The front was used as a show room complete with a waiting area fitted with rocking chairs, music, and a ladies toilet room. A private office was located in the rear. The work shop contained over $3000 worth of machinery and shop equipment to work on Ford cars, trucks, and tractors. The motto of Platt Brothers Garage was: "If your motor gets to 'woolie-raring, give it prescription of Ford's quick repairing"

In February 1922, H. J sold the Ford garage to W.E. Jones of Jennings, OK and the business became known as Perkins Motor Company.

During WWII, he was in California, in defense work. It was at this time that he met and married a woman named Lillian. Later they divorced and after WWII in Oklahoma he married Agnes Kirkwood, a milliner. He was the Willis Jeep dealer in Enid, OK, where his workshop was so clean you could eat off the floor! Agnes & H.J. stayed in Enid until 1962 when he moved to Denver and started working in his sister Elizabeth's real estate office as a salesman. It was in Denver that he suffered a fatal stroke, December 6, 1962. He was 71. Agnes survived him a number of years, living in a nursing home in Denver, with Elizabeth as her guardian. H.J and Agnes are both are buried in the Odd Fellows cemetery at Maramec, Oklahoma.