When I was researching These Fevered Days, I kept a “dailiness” file filled with particulars about Emily Dickinson’s world. Dickinson was a great doodler, for example, and excelled in catching mice. She loved ice cream and her mother’s fried donuts, and made fun of her sister’s snoring. The poet wrote on whatever was handy, including a flier advertising lavender cordials. I also saved details about Dickinson’s family: her father’s constant worry about wet feet, tumbling woodpiles, and aggressive cattle hooking his children; a description of the poet’s beloved Amherst evoking the town’s mixture of refinement and runty charm, “A village church with pillar’d front,” she wrote, “decked off in taste and elegance, except a little squat.”

I made note, too, of an incident involving Emily’s girlhood friend Helen Fiske, who, years later, would become the celebrated writer Helen Hunt Jackson. Helen jabbered so much at school she once had to sit for 20 minutes wearing a dunce cap with a corncob between her teeth. I liked the detail because it revealed Helen’s spunk, and offered a vivid warning to girls with much to say.

Around the time Helen sat with the corncob, Emily vowed to devote herself to a year of improvement. She cautioned a friend against letting her “free spirit be chained,” and teased her brother about who the real writer in the family was. “I’ve been in the habit myself of writing some few things,” she informed him. She also told friends she had been “dreaming a golden dream” and had dared to do strange and bold things, without asking anyone’s advice. Given all the stereotypes of Dickinson as a shy, submissive waif, what struck me was Emily Dickinson’s drive. She wanted to make her family proud, and she wanted to be famous.

Dickinson cautioned a friend against letting her “free spirit be chained,” and teased her brother about who the real writer in the family was.

One incident in particular revealed the fire in Emily Dickinson’s belly. It was winter. Emily had just turned 18, and she couldn’t get an earlier conversation with her cousin out of her head. “I have known little of you, since the October morning when our families went out driving, and you and I in the dining-room decided to be distinguished,” she wrote. “It’s a great thing to be ‘great,’ Loo, and you and I might tug for a life, and never accomplish it, but … What if we learn, ourselves, some day!”

Emily Dickinson did learn, or maybe she knew all along. By the end of her life she had composed nearly 1,800 poems, some of the most dazzling verse in the English language. If she caught a glimpse of her friend Helen Fiske that day sitting with corncob in mouth, perhaps young Emily absorbed a lesson the teacher hadn’t intended. “They shut me up in Prose—” one poem later began. “Because they liked me ‘still.’” But Emily Dickinson was a country girl. She had seen her share of corncobs. And she already knew corncobs—or anything else—would be no match for the determination, independence, and ambition growing inside her.

Martha Ackmann’s These Fevered Days: Ten Pivotal Moments in the Making of Emily Dickinson is out now from W. W. Norton & Co.