Her "Tempered Wires" wound up in a collection of 1935's best short stories. An essay about the delights of mayonnaise won her a $100 prize. She had long worked on a novel about the family's life in California's redwood forests.
But a five-page, double-spaced typed manuscript from 1930 was the stunner - a "juvenile" story her grandmother titled Amusement Trains.
Clipped to the top was a rejection letter from the New York publishers Platt & Munk, who'd had great success with The Little Engine That Could. Underneath, her grandmother had typed "written to be illustrated."
Now Johnson knew just what to do. She'd spent 30 years teaching elementary school in California, Germany, and here, and was a competent artist. She'd illustrate the story herself and give copies to Dahlgren's 13 grandchildren and great-grandchildren for Christmas.
She didn't dream Amusement Trains would find a larger audience. The tale turns out to be a parable for our times.
The story concerns two brother trains in an amusement park during the Depression. Freddy takes children around the grounds on a circular track, slow and steady. Flash rides the roller coaster, fast and brash.
But Flash's popularity takes its toll. His paint peels, his wheels squeak, he begins to rust. The park owners take him out of commission, and he can only watch as kids pile on his brother. When the owners decide they need a new train, will they remember Flash?
The story resonated with Johnson, who'd lost her job teaching music in 2008 when Episcopal Academy moved. She tried drawing several panels - "awful," she says.
Then one morning in August at Springfield High School's pool, Johnson learned of the illustrations Sueli Melo Vieira made for Adam Smith's The Wealth of Nations.
She decided to collaborate with her fellow swimmer. Vieira, too, was drawn to the tale. She'd moved to Philadelphia from Brazil to import cashews, then left her job when her boss made her report to his young son.
Over two months she drew - 22 colorful, cartoony panels. Friends reading over her shoulder wanted to know the story's ending. She sensed commercial possibilities and contracted with Amazon.com's Create Space to self-publish the book. The first 90 copies are to arrive this week.
Friday, the night of Jenkintown's tree lighting, they gave a reading at the Rhinoceros toy store, inviting a packed house of children to accompany them on train whistles, blocks of wood, a ship's bell, a triangle, and boxes of Good & Plenty for chug-chug sound effects.
"They did so well," said owner Kate Pettit, who said her first-grader "loved it."
Johnson and Vieira ended their performance with a song they wrote about persistence, how journeys can take different tracks.
"The message that comes from the Depression is a powerful one," says Vieira. "What her grandmother came up with 80 years ago is, 'Maybe we can't use you as roller coasters anymore. But we can recycle you and you can also be little amusement trains.' It works today."
Find more about the book at www.freddyandflash.com/epk.html
Contact Daniel Rubin at 215-854-5917, email@example.com, or @danielrubin on Twitter. Read his blog at philly.com/blinq