Just as fashion from 1960 differs from that of 1970 and 1980, so clothing changed in early America. Wardrobe staff papered their workspace walls with research diagrams showing the changes in clothing style from the 1790's to the 1800's to the 1820's: waistcoat, collar, bustle, wig, hat, and hemline sizes adjusting over the years. Some costume props would be rejected on authenticity grounds: "no no no wrong year."
The Dockside Artist character, sketching the scene from a warehouse loading area as Adams' ship arrives, picked up some of the real oyster shells which littered the ground and used them to supplement his existing supply of paint cups - an improvisation which real street artists of the period might employ.
History buffs might recall that a British Navy surgeon shortly before 1750 concluded that sailors, by sucking on limes, could reduce the incidence of painful and debilitating scurvy. Concurrent experiments involving sailors taking vinegar or sea water failed. Eighteenth century medicine was unaware that limes contained Vitamin C (a substance not really understood until the 1930s) and also did not fully comprehend scurvy as a nutritional disease, but crews were issued limes in their rations after the field study. British sailors and later British people generally were nicknamed "limeys" shortly afterward. At the film's dock set, around a peck of sucked-on cut limes litter the ground as if discarded by sailors.
For a more authentic look (and smell) of a real working quay, around two truckloads of oyster shells were heaped around the set of the Dockside Welcome Home Mr Adams Scene. Also present near a fishing shanty are several large real dried fish and at least one dried skate-ray.
Lest any modern straight (and sometimes bleached) teeth appear on camera, every last extra in the cheering crowd at George Washington's inauguration got their teeth painted with special fast-drying saliva-proof "gunk" paint. Working-class characters were given proportionately worse-looking smiles than the merchants and aristocrats.
Because the dock scene was filmed on back lot on dry land, an important informal crew job was "ship hose-person"; in order to look properly wet, the ship's hull facing the cameras needed an occasional vigorous spray with a garden hose.
During George Washington's inauguration, the apparent cheering crowd of thousands was actually filmed with only around 80 people. They would stand in a square formation - edged by greenscreen cloth (the material TV weathermen use as backdrops because it turns invisible on camera so that digital backgrounds can be added). After filming a few seconds of giddy flag-waving, the 80 would switch positions, trade flags and buntings around, pick up different things (pitchforks, tankards, children, etc) and move over thirty feet. More cheering. More filming. Repeat. By day's end there were enough squares of different-looking crowd activity to stitch the lot together digitally and make it look like a seamless mob of thousands.
While Adams' last words were reportedly "Jefferson survives", in reality Jefferson had died several hours earlier. Adams never received the news of his death. And while "Jefferson Survives" was apparently his last eloquently spoken words, his actual last words was a panicked cry of help to one of his grandchildren before he died.
During the scene in which Nabby has her surgery and John Adams is nervously pacing downstairs, Abigail says to him, "For god's sake, John, sit down." This is a particularly memorable line from the first song in the musical "1776" (music and lyrics by Sherman Edwards and book by Peter Stone), about the writing and signing of the Declaration of Independence.
During an interview on NPR's "Fresh Air," Paul Giamatti told interviewer Dave Davies that the scene in which Abigail and John have sex upon being reunited after many years apart was not written as a sex scene. The script only called for John and Abigail to kiss, but Giamatti said that he and Laura Linney discussed between themselves that they thought the characters would go farther in that situation, and they decided to "keep going" and hope the director and camera person would follow them, which they did. The scene they improvised and shot was originally much longer than what ended up in the finished film.