Golden Age is a literary phrase going back to Hesiod and his didactic poem Works and Days. Within is a reference to the ages of man, of which he counts five; The first being the Golden Age, the second Silver, the third Bronze, the fourth the Heroic Age and finally his own which was Iron.

The Golden Age of Television describes a confluence of events which allowed that medium to overtake its rivals. There are many, but I will restrict this answer to what I see as the largest.

It began with many popular entertainers transitioning from radio to television with tremendous success, such as Jack Benny and Red Skeleton. The trend was further abetted by unique and innovative content, such as the dramatic anthologies of Westinghouse Studio One, The US Steel Hour, Alcoa Hour, Kraft Television Theatre, and Playhouse 90. The coup de grace, however, were certain technological advances which lead to the supremacy of the medium. Prior to the '50s everything broadcast had to be either shot live or filmed, leaving news and sports very challenging undertakings better covered through print and radio. With the creation of videotape, however, content could be captured and edited in house then broadcast later while still appearing in every way to be live.

There are other factors worthy of investigation, such as the explosive post-war growth of the suburbs, the investigation into monopolistic practices of major film studios, such as with Paramount which lost decision in an antitrust case involving price fixing, as well as the effects of the inquests undertaken by the House Un-American Activities Committee. No answer could be considered complete which does not at least touch upon these elements.

Still, though the causes may be myriad the results are clear enough. Between 1949 and 1969 the number of households which had a television rose from one to 44 million, the number of commercial TV stations from 69 to 566, and advertisement spending grew from $58m to $1.5bn.

I am sure a more comprehensive and complete answer will follow, but until then hopefully this will prove helpful.