Corea and Korea
http://chronicle.nytlabs.com/?keyword=korea.corea.korean.cor...
Some history: "Corea" was more common in the English speaking world for the territory we call Korea today. At some point during the Japanese colonial period, as Japan solidified its ownership of the territory, the preferred spelling in English speaking countries became "Korea". ("Corea" is still used in many other languages and neither the Koreans nor the Japanese use Korea or Corea when talking about the peninsula).
There's a conspiracy theory that one of the cultural suppression activities the Japanese colonial government took part in (along with forcible language conversion and various geomanctic engineering efforts like driving thousands of iron poles into the ground at traditional seats of Korean power and moving entrance gates to palaces to break the flow of Chi) was broadcasting out to the world that "Korea" was the preferred spelling since it put Korea after Japan in alphabetized lists of countries in English speaking territories.
More pragmatically, both spellings were used up until the 20th century. But Korea was relatively unknown in the West outside of mild curiosity. The actual popularization of one spelling over the other seems to be the result of writings on Korea by the U.S. missionary and later consul general at the time, Horace Newton Allen, who exclusively used "Korea" when writing about the country.
This spelling was picked up and at the World's Columbian Exhibition in Chicago in 1893, the exhibit listed both spellings as correct, but people were generally told that "Korea" was the preferred spelling. Allen was heavily involved in the planning of the exhibit.
On the graph here, you can see that Korea wasn't a topic at all in the NYTs reporting until directly after the exhibition, which seems to have been successful in bringing attention to the country. But the more familiar "Corea" was used until 1897, when it was pretty much dropped in favor or "Korea".
Interest stayed low until the Korean war after which the amount of reporting on the country steadily increased.