In the early days of journalism in the United States, the political opinion of the paper wasn't just on the editorial pages. Early publications had a clear slant and purpose. For instance, <em>The New York Post</em> was started in 1801 by Alexander Hamilton, with the intention of using the paper to promote the views of the Federalist Party. Then Benjamin Day introduced the idea of the penny newspaper, starting <em>The Sun</em> as a New York daily paper in 1833, for the price of just a penny. (That would equate to about 25 cents in today's economy.) It made the news accessible and affordable to everyone, and Day's paper reported lots of news in straightforward fashion. It was the first paper to report on events involving ordinary persons -- recording crimes, deaths, suicides, etc.
More and more, newspapers shifted to a broader, less partisan approach as a way of expanding their readership (and thus selling more papers). The editorial page of each newspaper thus developed as the space within the paper where the editorial staff's political viewpoint could be seen.
