What were joseph pulitzer and william randolph hearst well known pioneers of?

Both were pioneers of journalism.  Joseph Pulitzer created yellow journalism and was a publisher of the Hungarian Dispatch and the New York World.  He was also elected Congressman in New York and campaigned against big business and corruption.  He is best known for the Pulitzer Prize which began when he gave money to Columbia University in 1917 to honor achievements in journalism.  William Randolph Hearst created the biggest newspaper chain and was a big influence on American Journalism.  He owned the San Francisco Journal and the New York Journal.  Both he and Pulitzer competed with each other and this led to the mass circulation of newspapers.