What is the origin of the phrase 'Extra Extra Read all about it?

Answer 1

In the early days of newspapers, when newspapers were the primary method of delivering the news, when something big happened, the publisher would not only publish the normal daily paper, but would also publish an Extra. The newspapers were sold on the street, often by newsboys, who had a stack of papers and would sell them to passersby. When an Extra came out, they would chant "Extra! Extra! Read all about it!" to call attention to the fact that something big has happened, and an Extra paper has been published.

Answer 2

In the UK, street newspaper vendors in the late afternoon or evening would use the call 'Extra, extra, read all about it' to announce there was a 'breaking news' type story and it was thought to be so interesting that the newspaper publishers had run an extra edition over and above the usual ones to make readers aware of this important news story. In the process, the vendors and the publishers would obviously sell more newspapers and hopefully their readers might even buy a second copy of the paper that day or, if it was a scoop, the paper with the extra edition would be bought instead of the competition.