Josephine "Jo" March Bhaer, originally from Concord, Massachusetts, grew up as a spirited, unconventional tomboy in a financially struggling family during the American Civil War era. The second oldest of four sisters, she harbored early literary ambitions and disdained traditional feminine constraints, frequently using slang, wearing practical clothing, and cutting her hair short. Her childhood involved staging self-written plays, reading avidly in the attic, and working as a companion for her strict Aunt March to support her family, including the selfless act of selling her long hair to fund her mother's trip to their injured father.

A decade after her youth, Jo appears as a married woman running Plumfield, a school established in the farmhouse inherited from Aunt March. She is married to German professor Friedrich Bhaer, and they have two sons, Rob and Teddy. At Plumfield, Jo educates her children, nieces, nephews, and orphaned students like Nan Harding and the street-hardened Dan Kean. Her teaching philosophy blends experiential learning through nature, music, and play with firm moral guidance. She advocates kindness and forgiveness, offering second chances to rebellious students such as Dan despite his initial destructive behavior, emphasizing emotional growth alongside academics to nurture individuality.

Traces of Jo's youthful independence remain, tempered by maturity. Though more composed and adopting traditional roles as a wife and mother, she occasionally exhibits her former spiritedness, like riding a bicycle in a tomboyish manner. She identifies with Nan's rebelliousness, seeing her younger self in the girl, and encourages Nan's ambition to become a doctor. Her relationship with Dan evolves from stern correction to maternal mentorship, helping him channel his ruggedness into respect for nature and responsibility. Her marriage to Professor Bhaer is collaborative; both share school duties and support students like Nat Blake, patiently teaching the illiterate orphan to read.

The school serves as an extension of Jo's ideals, combining domesticity with progressive education. It accepts both genders and varied social backgrounds, including local boys and orphans. Jo balances household management with creative pursuits like organizing plays and museums, reflecting her ongoing artistic leanings. Her background influences her empathy: having sold hair for family needs and rejected a wealthy suitor, Laurie, for authenticity, she champions self-reliance and moral integrity. She advises female students on expanding opportunities beyond marriage, subtly advocating for women's autonomy.

Plumfield becomes Jo's lifelong legacy, symbolizing her journey from a restless girl to a nurturing educator who harmonizes her unconventional past with societal expectations.