I live in a city with a name that few people not from here seem to be able to spell correctly: Cincinnati
Despite being the home of the first professional baseball team, the headquarters of Procter & Gamble and Federated Department Stores (among other large firms), and part of the name of a popular sit-com (WKRP in Cincinnati, Cincinnati seems to be regularly misspelled in various creative ways.
Using Google Trends, I found out that the most common way to misspell this city's name is "Cincinatti," but other mistakes are also common:
Thankfully, the search frequency of the correct spelling - Cincinnati - is magnitudes higher than any of the misspellings, but it's interesting to see such widespread ignorance. Imagine that many people spelling it "Misisipi". OK, never mind.