Keynes mentions having printed out all of Wikipedia. As of this episode's airing (March 2018), it would require 2600 bound volumes of 500 pages each to do this (filling about 13 tall bookshelves).
The episode opens with a shot of the Millerson house in 1955. The US flag out front has 50 stars (the lines of stars can be seen to be staggered as the flag slowly waves) instead of the 48-star flag used in 1955. The 50-star flag was introduced in 1960 when Hawaii joined the Union.
The team drives along a rural road marked with a double yellow center line and white edge lines (also known as "fog lines"). In the mid-1950s, when this episode is set, double yellow lines were uncommon except on major highways, while fog lines had only recently been introduced on a trial basis in Connecticut.
The car shown in the black & white photo (first time near the beginning of the episode and again about halfway through) is a 1957 Chevy Belair. The time frame is 1955, and the first 1957s didn't hit the showrooms until September 1956.
Although set in the flatlands of Darlington, SC, there are huge mountains in many scenes. No pine trees or palmetto trees to be seen anywhere, either.
Towards the end of the episode, Emma berates Carol for not letting her kill Lucy in 1818, when she should have said 1918, as the previous episode was set in World War I.