Factual error: Season 1, Episode 4: New Amsterdam. At various stages of the discussion between Peter Campbell and his wife regarding the purchase of their coop apartment, they discuss down payments and mortgages. Although it may be possible to finance a coop today, in 1960 the buyer would have been expected to pay the total amount up front. This was still the case as recently as 1999, when I sold my parents' apartment after their death.

Factual error: The show takes place in 1960 and a calendar shows it to be March. At one point, Don Draper chews out Pete Campbell for stealing a discarded health report regarding cigarettes. Don tells him that there is nothing out there that will magically make copies of something (eluding that photocopiers hadn't been invented yet). In 1959, Xerox introduced the Xerox 914, the world's first plain paper photocopier. By the end of 1961, the 914 had generated almost $60 million in revenue. The series takes place in the biggest and best ad agency of New York City. If they didn't own one, surely they would know about the ad campaign surrounding it.

Factual error: When the new secretary is being shown around the office, the cover is slipped off an IBM Selectric typewriter. She is told not to be afraid of the new technology, it was made easy enough for a woman to use. The episode takes place in March 1960 (a calendar is shown) and the IBM Selectric wasn't introduced until 1961.

Factual error: The ad team is trying to come up with a new campaign for Lucky Strike cigarettes, since all health claims must be removed. With a stroke of genius, the slogan "It's toasted" is created and approved. "It's toasted" was the ad campaign that debuted in 1917. In the early 60s, it was "Lucky Strike separates the men from the boys, but not from the girls".