Over time, his dogged pursuit of high school results for the benefit of the AP membership in Virginia became well known. He was known to stop at nothing until he had a result for every game that was scheduled, and became familiar to local radio station employees and sheriff's departments in his pursuit of scores.
In 1954, Johnson used his downtime on the night shift to begin keeping a ledger of the year's basketball results with no idea that he was beginning a pursuit that, in some ways, defined him.
He kept the meticulous ledgers throughout football and basketball season until he retired on Dec. 28, 1983, already revered as the foremost authority on Virginia's prep sports history.
In 1986, a phone call reignited his love for records, and Johnson added research to his passion for his rose garden and the gardenias he grew in his backyard to share with friends and neighbors.
The caller wanted to know if Johnson could confirm that a player's 420-yard rushing total in a recent game was a state record, Johnson recalled in an interview with the AP in 1995, and he didn't know.
"The more I thought about it," he said, "the more I wondered, 'Doggone it, why don't I know?'"
In the ensuing two-plus decades, Johnson spent four or five mornings a week at the state library, researching team and individual records going back to almost 1900. He also was a regular visitor at the AP bureau in Richmond, combing through newspapers for information to keep track of the stars of the day.
"It took me over," Johnson said in the 1995 interview.
Without Johnson's effort, the records would not exist in Virginia, said Ken Tilley, executive director of the Virginia High School League.
"No person is more responsible for all the information that exists about high school sports in Virginia than Marshall Johnson," Tilley said Thursday, calling Johnson "the most influential person in high school sports in Virginia."
At the time of his death, Johnson had two four-drawer filing cabinets and eight boxes filled with hundreds of legal pads filled with his scrawl, much of it legible only to him, chronicling the prep history of schools, coaches and players he so painstakingly researched and updated after every season. He also kept meticulous records about state golf.
"He means so much to all of us that covered high school sports, and I've got as many fond memories of working with him at the Virginia State Open and State Amateur," said retired sports writer Arthur Utley, who covered prep sports and golf for the Richmond Times-Dispatch. "His knowledge about state golf was as good as his memory about high schools."
Each year until 2010, at season's end he would provide the AP and state newspapers a list of team and individual records that had been broken during the season without ever seeking credit for his work.
Every winter, as football season was winding down, he sent letters to as many as 50 coaches in areas without steady media coverage to inquire about players worthy of the AP's all-state consideration, trying to be sure no deserving player would be overlooked. When he became unable to continue that practice, coverage gaps made it impossible for the AP to continue confidently naming a deserving all-state team.
Hundreds of players earned all-state honors solely because of Johnson's efforts on their behalf.
Up until 2010, when Johnson's focus shifted to caring for his wife of 67 years, Shirley, he continued to cover all or parts of the VHSL basketball playoffs for the AP, and took time between each championship game to present the Marshall Johnson Sportsmanship Award, so named in 1984.
Each summer, he also attended the Virginia High School Coaches Association awards dinner to present the Marshall Johnson Media Award, named for him in the 1970s, to a journalist distinguished for their high school sports coverage.
"I was proud to win that award," Robert Anderson of The Roanoke Times said. "It wasn't because it said award on it. It was because it said Marshall Johnson on it."
Johnson also received the VHSL's Distinguished Service Award in 1984, was a charter member of the VHSL Hall of Fame and, in 1995, was in the charter class of media honored by the Virginia Sports Hall of Fame.
Johnson was preceded in death by his wife, Shirley Wright Johnson, in November 2012. To the end, Johnson loved to get together with friends from the sports and newspaper world and share, with a keen memory, stories about the exploits of the athletic teams at Washington & Lee and the state's other college programs from his days as a student throughout his distinguished career and beyond.
Johnson is survived by his son, Michael, of Fairfield Glade, Tenn., and his wife Jayne; his daughter, Patricia Edwards of Richmond; grandson Michael Johnson Jr. of Richmond; and granddaughters Stefanie Johnson Cooley of Kingsport, Tenn., and Robyn Johnson of Yakima, Wash.
Funeral arrangements are pending.