According to Official Guinness Records,
The 12-part An American Family (USA, PBS, filmed 1971;aired 1973) is considered to be the first TV show to feature a prolonged fly-on-the-wall look at real people. Over 10 million viewers would tune in each week to watch as the "stars" - the Louds, a typical nuvlear family from Santa Barbara, alifornia, USA - went about their everyday lives. Viewing figures peaked when mother Ann asked father Bill for a divorce.
For a complete list of 1971 records, please visit 1971 Guinness Records in United States.