Emily is a 19th-century American poet living in Amherst, Massachusetts. Born into an affluent family, she chooses relative solitude to focus on her intellectual development and poetry. She maintains a robust correspondence with newspaper editors and intellectuals, compiling hundreds of poems into booklets that explore technology, nature, and humanity.

The unnamed narrator of "I like to see it lap the Miles" acts as a subjective observer. The speaker catalogs the movements of a steam locomotive by comparing it to an untamed horse. Operating from a position of privilege, the speaker focuses on the awe of technology while largely overlooking the human labor that makes it possible.

The subject of Emily Dickinson's poem acts as a personified representation of rapidly expanding locomotive technology. It possesses immense physical strength, taking prodigious steps around mountains, yet simultaneously exhibits weakness by crawling and complaining. The machine serves as a docile worker that retreats to its stable once its journey concludes.

Austin is Emily Dickinson's older brother and a member of the affluent Amherst family. He is married to Susan Gilbert, who becomes his sister's closest friend. He remains a central figure in the Dickinson family's social and historical dynamic.

Lavinia, commonly called Vinnie, is the youngest sibling in the Dickinson family. She remains close to Emily throughout her life in Amherst. Following Emily's death, Lavinia plays the crucial role of discovering the vast collection of poem booklets her sister left behind.

Susan is Austin Dickinson's wife and a vital presence in Emily Dickinson's life. She maintains a deep, enduring friendship with the poet, serving as a direct social connection to the outside world.

Edward is the patriarch of the Dickinson family. Operating as an influential lawyer and politician, he actively campaigns for infrastructure development. He successfully gathers support for the Amherst Depot, which brings the railroad to their town and provides direct inspiration for his daughter's poetry.

Emily Norcross is the mother of the Dickinson siblings. Coming from a lineage of prosperous farmers, she works as a homemaker to maintain the affluent Amherst household for her husband and three children.

Mabel is a creative intellectual situated in the Amherst community. She forms a complex tie to the Dickinson family through a prolonged affair with Austin. She later takes on the monumental task of editing hundreds of Emily's poems to prepare them for publication.

Thomas is a prominent literary and military figure who publishes The Atlantic Monthly. He leads a regiment of Black Union soldiers during the Civil War and serves as a regular correspondent for Emily, providing her with an intellectual tether to the wider world.

Josiah is an editor for The Springfield Republican, the largest newspaper in New England during the period. He participates in a robust correspondence with Emily Dickinson, offering her a connection to the publishing sphere.

Samuel works as an editor for New England's largest newspaper. He serves as one of the few individuals outside of Emily Dickinson's immediate physical circle with whom she actively exchanges letters.

Samuel is the grandfather of the Dickinson siblings. Operating as an influential historical figure in the family's lineage, he contributes to the family's regional prominence by helping to establish Amherst College.

Boanerges is a biblical reference used by the speaker to describe the train. Originally the surname Jesus gave to the apostles James and John, it translates to "son of thunder," capturing the spiritual and striking force of the locomotive's sounds.