History of media bias
Via Instapundit, The History of Media Bias. Interesting thoughts on how the change from "a reporter works his way up" to "a reporter starts with a degree in journalism" may have affected that.
I can verify that once media bias was quite open, with no paper pretending to be objective. Arizona had its Democrat and its Arizona Republican, and their orientations reflected exactly that. Today the Democrat has long faded away, and the Republican became the Arizona Republic. In those early papers, one's editorials would respond to the other's, quite directly and even insultingly. It did make reading more interesting.