Abigail is an intellectually curious and resourceful woman married to ambitious country lawyer John Adams. She chafes against the domestic expectations of colonial Massachusetts. As political tensions rise, she manages the family farm, starts a mercantile business, and serves as her husband's key political informant. She fiercely advocates for women's rights and education, building a foundation of financial and emotional independence to survive a deeply unequal era.

John is a brilliant, principled, and sometimes temperamental country lawyer who becomes a central figure in the American Revolution. His deep patriotism and ambition drive him to the Continental Congress and later to diplomatic posts in Europe. He values his wife's counsel but frequently prioritizes his public duties over his family's immediate needs, expecting quiet sacrifice from those he leaves behind.

Jefferson is a brilliant and charming Virginian who serves as a diplomat and later as a political leader. He shares intellectual passions and a deep grief over the loss of children with Abigail. However, his radical democratic ideals and personal hypocrisies create an ideological chasm between him and the more moderate Adams family.

Hamilton is a highly ambitious and brilliant political operative who serves as the Secretary of the Treasury. He is a master of intrigue and strategic planning, prioritizing his own influence over party unity. His relentless political maneuvering makes him a dangerous antagonist to the Adams administration.

John Quincy is the serious and dutiful eldest son of the Adams family. He internalizes his parents' devotion to public service, maturing quickly as he accompanies his father to Europe. He acts as a steadying force within the family, using his diplomatic education to manage both international politics and domestic family crises.

Nabby is a quiet, dependable, and stoic daughter who serves as her mother's steadfast companion. Growing from a reserved girl into a dignified woman, she endures the restrictive social expectations placed upon her. Her romantic prospects and future are heavily dictated by her father's approval and her family's public standing.

Charles is a charming and sweet-natured son who struggles under the immense pressure of the Adams family name. Taken to Europe as a young boy, he lacks the stern self-discipline of his older brother. He attempts to study law in New York but proves vulnerable to the temptations of the city and the emotional toll of his father's long absences.

Tommy is the youngest Adams son, a plain and hardworking young man who frequently feels overshadowed by his prominent siblings. Unlike his brothers, he remains in America during the revolution, enduring difficult stays with relatives. He eventually takes on the management of the family's farm.

Mercy is a celebrated playwright, political satirist, and intellectual in colonial Massachusetts. She provides a rare model of female public engagement, bonding with Abigail over literature and the looming struggle for liberty. She acts as a mentor but sometimes clashes with Abigail over the differing sacrifices their families make for the revolution.

Phoebe is an enslaved woman who serves Abigail's family and acts as a pragmatic confidante and second mother figure. She possesses a deep wisdom about the realities of power and dependence, offering Abigail blunt advice about surviving within an unequal marriage. She eventually secures her freedom under the Massachusetts constitution.

Colonel Smith is a charismatic military officer who courts and marries Nabby Adams. While initially appearing as a suitable and honorable match, his wounded pride and reckless financial speculations eventually cause significant trouble for his family, demonstrating the precarity of a woman's dependence on her husband's character.

Washington is the revered commander in chief of the Continental Army and the first President of the United States. He is a unifying figure whose physical health is closely tied to the stability of the fragile new nation.

Martha is the nation's first First Lady, setting the precedent for public receptions and social protocols. She forms a bond with Abigail over the unique burdens of their public roles and the shared grief of losing children.

Dr. Tufts is Abigail's kinsman and uncle who serves as her trusted agent in Boston. He facilitates her covert business investments, helping her purchase land in Vermont using her secret earnings.

Susanna, nicknamed Suky, is Abigail and John's infant daughter. Her chronic health struggles highlight the fragility of life and the devastating domestic toll of the era's medical realities.

Sally is an enslaved teenager in the Jefferson household. Her arrival in Europe exposes the deep moral hypocrisies of the American founders, prompting Abigail to quietly support what she suspects is an attempt by Sally's mother to secure her freedom.

Polly is Thomas Jefferson's young daughter who is reluctantly sent across the Atlantic to join him. Her distress upon arriving in Europe solidifies Abigail's belief that great statesmen often fail in their duties as fathers.

James Lovell is a delegate who serves as Abigail's primary source of information when John is unreachable. His letters contain increasingly inappropriate flirtations, causing Abigail to eventually sever their correspondence to protect her reputation.

Sally is Colonel Smith's sister who marries Charles Adams. She endures immense suffering as she attempts to support Charles through his rapid descent into addiction and financial ruin.

Royall Tyler is a handsome young lawyer who wins Nabby's heart during the revolution. His character comes into question due to rumors of harsh behavior and subsequent infidelity, leading to a painful broken engagement backed by John Adams.