In some episodes, Abigail wears low cut dresses

One scene where John Adams walks in on Benjamin Franklin and a woman while they are in the bath playing a game of checkers. The scene is played for comedy and there is no nudity involved, with the exception of some possible nude paintings on the wall.

A couple have sex a couple of times in the show, though they are clothed and it is cut short before anything explicit happens.

E1, 50:34 - A man is stripped naked, tarred and feathered in front of a crowd. Brief glimpses of his genitals and behind. Non-sexual.

E7, 7:14 - We see a woman's breast twice in a medical context due to a breast amputation surgery.

A few sexual references, mostly mild. When Benjamin Franklin and John Adams visit France, there are some innuendos exchanged during a dinner. Also references to prostitutes.

A character is seen bloodletting and can be quite disturbing

A battle between two ships at sea. They fire cannons at each other. One ship is hit on deck and several men are blown to bits with a lot of blood. One man's leg is nearly torn off. His is screaming pain and blood covers the deck. They carry him screaming downstairs to under deck where they amputate it. We can clearly see the saw cutting through his leg and he screams. Blood splatters everywhere. A child watches. This scene is very disturbing, intense and very gory.

British soldiers fire a volley of rounds into innocent American citizens (not too much blood).

A family watches a battle between Americans and British in the distance, with cannonfire. The Americans are shown to have lost and retreat by the family's home. Several of them are severely wounded with bloody bandages.

A man is stripped, tarred and feathered (see sex/nudity for more detail). The scene is disturbing albeit historically inaccurate.

A few mild obscenities (damn, hell, bastard)

Several characters drink and smoke pipes.

A couple of instances where they get mildly drunk.

A man suffering from smallpox is seen. It's rather graphic and a physician cuts pustules from him to inoculate people with.

The amputation scene is very intense.

A woman has cancer in her breast and the doctor says he must surgically remove it (see the sex/nudity for more details).

The tarring scene is intense and disturbing albeit historically inaccurate.