Truly, "Pittsburgh" might be America's most misspelled city. It is one of the few U.S. cities or towns to be spelled with an "h" at the end of a burg suffix.
Originally Fort Duquesne, the earliest known reference to the new name, Pittsburgh, is in a letter sent from General John Forbes to William Pitt the Elder, 1st Earl of Chatham, dated November 27, 1758. This letter notified Pitt that his name had been given to the place, spelled "Pittsbourgh." In the city charter, granted on March 18, 1816, the Pittsburgh spelling is used on the original document, but due to an apparent printing error, the "Pittsburg" spelling is found on official copies of the document printed at the time.
In 1891 the United States Board on Geographic Names adopted thirteen general principles to be used in standardizing place names, one of which was that place names ending in -burgh should drop the final -h. At this time the city's name was rendered "Pittsburg."
The Board supported its decision to rename Pittsburgh by referencing the printed copies of the 1816 city charter which featured the spelling Pittsburg rather than Pittsburgh. Based on those copies, the Board claimed that the official name of the city had always been Pittsburg. However, the members of the board seem to have been unaware that the original 1816 charter specified the name of the city to be Pittsburgh, and that only the copies of the charter featured the erroneous spelling "Pittsburg."
The new official spelling was resisted by many people in the city. The Pittsburgh Gazette refused to adopt the Board's decision, as did the Pittsburgh Stock Exchange and the University of Pittsburgh. Official city documents continued to use the old spelling. Responding to mounting pressure, the Board reversed the decision on July 19, 1911, and the Pittsburgh spelling was restored after 20 years of contention.
Many cities across the United States named after the city of Pittsburgh, such as Pittsburg, Kansas and Pittsburg, California continue to use the "Pittsburg" spelling in their names. Other independent municipalities, such as the borough of East Pittsburgh, Pennsylvania, reflect the modern spelling.