The action takes place in Philadelphia in May, June and July of 1776. American troops have been fighting the British for a year, but the Continental Congress in Philadelphia has not yet declared independence. John Adams of Massachusetts is fed up, but then most of his fellow delegates are fed up with him ("Sit Down, John"). Exasperated, he takes his case to the Almighty ("Piddle, Twiddle And Resolve"). On the human side, Adams has been long separated from his wife, Abigail. Their letters and his imagination bring them briefly together ("Till Then"), he demanding that the women of Massachusetts send saltpeter for gunpowder, while she demands that Adams convince Congress to send sewing pins to the ladies.
Pennsylvania's Benjamin Franklin sees that Congress's dislike for Adams is holding back the cause of independence. Franklin persuades Adams that Richard Henry Lee of Virginia should be the one to propose independence. Lee rides off to secure the support of his legislature, after bragging about his family ("The Lees Of Old Virginia").
It is now June. Couriers bring to Congress dispatches full of bad news from General Washington. Lee returns and proposes separation from Great Britain. John Dickinson of Pennsylvania opposes. An extremely contentious ensues, leading even to a (brief) physical fight between Adams and Dickinson.
With the colonies evenly divided — six to six, with New York abstaining, as it does on all votes — Dickinson proposes that any resolution on independence must be unanimous. This resolution passes after John Hancock, president of the Congress, is called upon to break the tie. Although he supports independence, he votes in favor of unanimity on the principle that any colony that votes against independence will be forced to side with Britain and fight with them, thus setting Americans against Americans in combat.
As a delaying tactic, Adams proposes that the vote be postponed until a declaration of independence is written. Dickinson mocks the proposal as a desperation tactic, but it passes. A committee is formed to write the declaration, but no one wants to do the writing ("But, Mr. Adams”). A reluctant Thomas Jefferson, who had been about to take a leave from Congress to visit his wife at home in Virginia, is enlisted.
Jefferson, however, has writer's block, owing to his long separation from his wife, Martha. Adams can empathize as this reminds him of his own loneliness. After a meeting with Jefferson to gauge his progress, which is nonexistent, Adams again conjures up Abigail. They express their mutual desire to be reunited ("Yours, Yours, Yours").
Adams sends for Martha, believing that once Jefferson's problem is solved, he will be able to write the declaration. Martha arrives, and the Jeffersons immediately take to his bedroom. The next morning, after she emerges from the connubial apartment, she explains to Franklin and Adams how Jefferson won her heart ("He Plays The Violin").
Congress is stalemated. A delegation is sent to inspect the army at New Brunswick, expecting the worst after a dispatch from Washington describing a disastrous scene there, including prostitutes and an outbreak of the French disease. Adams enlists Samuel Chase of Maryland, a skeptic on independence, to join him and Franklin on their trip to New Brunswick. Adams believes that, despite Washington's report, Chase will be convinced that it is the very unruliness of the troops that will win the fight against England.
Now we get a closer look at Dickinson and his fellow Conservatives, freed briefly from the torments of Adams and Franklin: These delegates don't want independence from Britain, or indeed change of any kind ("Cool, Cool, Considerate Men:). After they depart, Washington's courier tells Congressional custodian Andrew McNair and a "leather apron" in the employ of Congress about his own experience on the battlefield seeing two of his friends shot down and how their mothers then searched to find the bodies of their dead sons ("Momma Look Sharp").
Adams and Franklin return from New Brunswick just as Jefferson's completed Declaration of Independence is being read, while Chase is on his way to Maryland to convince the legislature that the army can win against England. Adams, Franklin and Jefferson sit in the Congressional antechamber, waiting for the reading of the Declaration by Congressional secretary Charles Thomson to conclude. They debate among themselves which bird should be the symbol of the new country ("The Egg").
Just when it seems all objections to the Declaration have been resolved, and it can finally be voted on, South Carolina's Edward Rutledge stands. The Declaration calls for the freeing of all slaves. The South will not have it. And lest the proto-abolitionists from the North point fingers, Rutledge reminds them ("Molasses To Rum") that the "triangle" trade enriches Boston as much as Charleston. He and the Southern delegates walk out.
Adams fights against removing the abolition clauses from the document, but finally relents. In despair, he conjures up Abigail, who assures him that he deserves the great respect with which she regards him. Suddenly, saltpeter from the ladies of Massachusetts arrives, and Adams sends McNair out to buy sewing pins to send to the ladies in return.
Left alone, Adams wonders if he anyone shares his vision of an independent America could be ("Is Anybody There?").
July arrives; and the delayed vote must be taken. With the clause that would free the slaves deleted from the Declaration, Rutledge votes in favor, bringing North Carolina, which always defers to South Carolina, with him. Only Pennsylvania still votes no, since the third delegate, James Wilson, has hitherto sided with Dickinson. Adams and Franklin persuade Wilson that if he provides the deciding vote against independence, he will go down in history as the man who prevented American independence. Wilson changes his vote, and Pennsylvania votes in favor. The delegates sign the Declaration (Finale).
(Adapted from the synopsis on the Masterworks Broadway site.)