Short answers, pulled from the story.
The first ITV service to launch was Associated-Rediffusion on the 22nd of September 1955. This event marked the end of a nineteen-year monopoly held by the BBC Television Service which had been established in 1936.
Granada Television remains the only franchisee to stay an ITV contractor since the creation of the network. The Granada studios closed in 2013 after decades of service while WWN became the only operator declared bankrupt in 1963.
All fifteen regional licences are now held by just two companies: ITV plc and STV Group. ITV plc holds the majority of these licences through its subsidiary ITV Broadcasting Limited as regulated by Ofcom.
The origins of the new network lie in the passing of the Television Act 1954. That legislation created the Independent Television Authority to award franchises and regulate the industry heavily to break the monopoly on television held by the BBC.
ITV became the exclusive free-to-air home of British racing starting the 1st of January 2017. Prior to this date the network had covered Formula One from 1997 to 2008 and returned to boxing in 2005 before stopping coverage entirely by 2010.