Pittsburgh has been spelled with an "H" officially and historically since its founding in 1758, except for the period between 1890 and 1911.

"How to Spell Pittsburgh"
Reprinted from Pittsburgh First, the Official Organ of The Chamber of Commerce of Pittsburgh, 23 July 1921.

Whether to write Pittsburgh or Pittsburg is a question which recurs with what seems surprising frequency until one remembers that each year the industries and other interests of Pittsburgh bring to the city large numbers of people who are not acquainted with the history attached to the name, or with the official decisions which have been made concerning the way in which it should be spelled.

In 1911 the spelling with the final "h" was officially restored after a period during which the United States Post Office Department, following the United State Board of Geographic Names, had dropped the final "h." Through the efforts of interested citizens, there was started a movement which ended in official recognition of the spelling "Pittsburgh." The findings of that committee appointed at that time to investigate the historical aspects of the question are reprinted here.

The only historically correct spelling of the word Pittsburgh, as designating the city located at the confluence of the Allegheny and Monongahela Rivers, is with the final "h." In 1768, the descendants of William Penn, the original proprietor of the land known as Pennsylvania, purchased from the Indian tribes known as the Six Nations, lands situated in the Western part of this state, and including the land covered by the present City of Pittsburgh.

In 1769, a survey was made of the land situated between the two rivers, which the Penns had reserved to the private enjoyment of the proprietaries, and which they called the "Manor of Pittsburgh."

In 1784, the laying out of the "Town of Pittsburgh" was completed by Thos. Vicroy of Bedford County and approved by the attorney of the Penns in Philadelphia. The Act of March 5, 1804, which modified the provision of the old charter of the Borough of Pittsburgh in 1794 -- the original of which is not in existence, so far as known -- refers throughout to the "Borough of Pittsburgh."

The Act of March 18, 1816, incorporated the City of Pittsburgh. The original charter was burned when the old Court House was destroyed by fire. In the Act incorporating the City of Pittsburgh, the "h" is used. In printing this Act in one of the law reports, the "h" was evidently dropped by the printer. The ordinance for the organization of the City of Pittsburgh after the passage of the Act of 1816, and recorded in ordinance book, Vol. 1, page 1, with the seal of the City of Pittsburgh attached, is uniform in the use of the "h."

"All May Assist Nation-Wide Campaign How to Spell Pittsburgh"
Reprinted from Pittsburgh First, the Official Organ of The Chamber of Commerce of Pittsburgh, 23 July 1921.

Patriotic Pittsburghers will assist in educating the public in the correct spelling of the name of their city. The "h" is all important, and distinguishes the Pittsburgh in Pennsylvania from other towns of the same name in various parts of the country. The report of the Chamber's Committee on Education, May 7th, 1908, published several times in Pittsburgh First, has been reprinted in folder form and may be had in large quantities by all who desire to assist in the campaign. Members of the Chamber particularly are invited to enclose the folders in their mail addressed to other cities. The folder has been sent to the news editors of the leading daily newspapers throughout the continent asking their co-operation in the correct spelling of Pittsburgh. They will be sent a few weeks later to the heads of all the educational institutions of the country as well as the superintendents of public instruction in all the states.

Throughout all the country there has been an improvement in the spelling of Pittsburgh. "The Literary Digest," for many years an offender in this regard, has added the "h" and consistently adheres to this style. The New York Herald and Sun, in response to a request from A. H. Childs, of this city, has corrected its spelling upon the especial order of Frank A. Munsey, who asked that the same rule be applied in all Munsey publication offices. A canvass of letters received from out of town in the mail arriving at the Chamber of Commerce over a period of six consecutive days showed 73 letters out of 100 correctly spelled. In another lot of 100 letters from out of town, received in one day's mail, the score was 77 correct; 23 without the "h."