Those aren’t the kinds of things the OP is talking about.
I read this somewhere else on the Straight Dope, so take it with a grain of salt.
U. S. Grant was born Hiram S Grant. The S didn’t stand for anything on account of being named after two relatives who’s first name began with S. When he enlisted in West Point the army erroneously thought the S stood for Simpson, since that was his mother’s maiden name. He later changed his name to Ulysses Sampson Grant.
I didn’t find out until quite recently that the “From Hell” letter reportedly written by Jack the Ripper was actually fabricated by a newspaper.
Where did you learn that? I thought that the writer of the From Hell letter is, and has always been, unknown. 
The bolded sentence actually applies to Harry S Truman. As for Grant:
It’s true that Simpson was his mother’s maiden name. His “homepage” states (without citing a reference):
One of my favorites, quoting from wikipedia:
“The number of human chromosomes was published in 1923 by Theophilus Painter. By inspection through the microscope, he counted 24 pairs, which would mean 48 chromosomes. His error was copied by others and it was not until 1956 that the true number, 46, was determined by Indonesia-born cytogeneticist Joe Hin Tjio.”
There’s the whole Columbus and the “Indians” thing, which has lasted a pretty long time…
Speaking of Indians: Gypsies (Roma) are from India, not from Egypt.
And less because a lot is bound up by oxalates.
But the original Popeye ate sweet potatoes not spinach. 
Though hundreds of letters claiming to be from the killer were posted at the time of the Ripper murders, many researchers argue that the “From Hell” letter is one of a handful of possibly authentic writings received from the murderer.
You are so very close to being correct, however. The “Dear Boss” letter seems to have been a journalistic hoax.
Nome, Alaska name.
A British officer making a chart wrote “Name?” next to this village when he didn’t know the name. The mapmaker read this as “Nome” and put that down as the name of the village, and it’s stuck since then. The town tried to change it’s name once, but the US Post Office refused to accept that.
(There’s another theory that this village was named after the Nome valley in Norway, which was somewhat near the birthplace of the towns’ founder. But that’s much less fun.)
Arab, Alabama vs. Arad, Alabama.
The name of the town was an unintentional misspelling by the U.S. Postal Service in 1882 of the city’s intended name, taken from Arad Thompson, the son of the town founder and first postmaster Stephen Tuttle Thompson. Two other names for the town were sent to the Postal Service for consideration: “Ink” and “Bird”. Arab has frequently been noted on lists of unusual place names.[4]
from Wiki: https://en.wikipedia.org/wiki/Arab,_Alabama
In a similar vein, the current distance of 60’6" from home plate to the pitcher’s rubber was due to misreading the intended distance.When the dimension was changed from 50 feet in 1893, it was supposed to be 60 feet even, written as 60’0", but the zero was read as a six and the mistake stuck.
Not propaganda but misinformation to disguise RADAR.
It’s not completely false–vitamin A is necessary for vision. For a person with low vitamin A levels, eating carrots will improve their eyesight. But once you reach the needed level, additional vitamin A does not improve your eyesight.
The New York Times account of the 38 witnesses who saw Kitty Genovese being attacked for half an hour but didn’t bother call the police is completely false:
https://web.archive.org/web/20070510003952/http://www.oldkewgardens.com:80/ss-nytimes-3.html
That’s a good one.
There’s also “the woman who sued McD’s and won millions as her coffee was too hot”
" a 79-year-old woman who suffered third-degree burns in her pelvic region when she accidentally spilled hot coffee in her lap after purchasing it from a McDonald’s restaurant, ultimately Liebeck was only awarded $640,000. Liebeck was hospitalized for eight days while she underwent skin grafting, followed by two years of medical treatment."
Coffee was dangerously hot, McDs had been warned, she suffered serious injury and collected less than a million.
Does the Drake Equation qualify?
Everyone ‘knows’ that the Drake Equation is used to calculate the probability of life in the universe. And by plugging a few numbers in, it is basically proved that there must be countless civilizations out there.
In fact it was produced as a discussion paper at the initial SETI conferences - designed to stimulate ideas about how best to search for any detectable communication transmissions from other sources.
The initial report was that “Mama” Cass Elliot of The Mamas and the Papas choked to death on a ham sandwich. She was very obese so it was easy for people to believe in a negative way. In fact she didn’t choke on anything; it was her heart that gave out. However many people from the Baby Boomer generation believe that choking while eating did it.