Hop Up magazine popularized the "little pages" (trade-sized or pocket-sized) magazine format (5-1/2" by 8"). It was started by Road & Track magazine staff who observed the popularity of hot rods & customs and felt a need to cover local cars and events. The first issue in July, 1951 was a test run, and August was the first full production run. It was 48 pages and priced at $.15 each. Note that both July and August issues share the same cover and volume and series number.
In 1952, the Road & Track advertising manager and investor Bill Quinn traded his invested shares for the rights to the Hop Up title, and he took some staff to form the new Quinn Publishing Company in Los Angeles. The magazine struggled financially due to its small size and lack of advertisers, so in February, 1953 Hop Up went to a larger print format. (Note: Readers wrote and complained about the change, so Quinn assigned Spencer Murray to create Rod & Custom in the small format style. This decision gave birth to both Rod & Custom and to Honk).
Bill Quinn really wanted to compete with Motor Trend, so in June, 1953 Hop Up was co-titled as Hop Up and Motor Life. The content began shifting to new cars, and the February, 1954 issue was the last one with this co-titling. Hop Up was dropped from the title in March, 1954, and content moved to Rod & Custom.
And in the last twist of fate, Bill Quinn sold Rod & Custom and Motor Life magazine titles to Petersen Publishing in June, 1955