The answer will depend on whether you are considering licensed releases only or if you are also including shows that have fallen into the public domain. If you include the latter, I'd hazard a guess and say THE LONE RANGER. I have some public domain episodes of the RANGER that date back to the Fall of 1949 in terms of their original broadcast dates.
If I see this, I might buy it for laughs, in Walmart.
Dangerous Assignment (Classic TV Series) Special agent Steve Mitchell travels the globe and encounters action and intrigue in four thrilling episodes of this classic TV series.
Starring: Brian Donlevy
DVD Details:
*Run Time: 103 minutes *Number of Discs: 1 *Originally Released in *1949* *Black & White *No region encoding; For global distribution.
Description by Oldies.com:
Join Steve Mitchell (Brian Donlevy) in this suspense filled series of danger and espionage, as he travels across the world on assignment for the United States Government. Agent Mitchell unravels the sinister plots of those seeking the downfall of peace and democracy.
Mine Story: Mitchell journeys to the volatile Middle East to investigate the assassination of an Arabian leader.
Incident: A dangerous web of intrigue and deceit unfolds as Mitchell searches for a missing diplomat and his daughter.
Art Treasure: A trail of bodies leads Mitchell on a train ride into danger, as he pursues art thieves holding the key to a stolen Nazi fortune.
Manager Story: A European scientist desperate for the safe return of his son gives Mitchell information that may lead to the capture of an international spy
I think the oldest TV show on VHS was an experimental one and could be considered a special presentation: A live feed of the 1939 World's Fair in New York, with a speech by President Franklin Roosevelt. Not sure if it was released on LD (laserdisc) or DVD though.
I would like to buy old TV shows. Even public domain. Mostly detective and westerns. Its only the Beverly Hillbillies where I don't like public domain because they are not played in the correct order.
I would like old cop TV shows, such as Dragnet and The Untouchables.
Tom, you mentioned "Dangerous Assignment" in one of your posts. This was an early spy series. You can get 20 (of 39) episodes on a 3-DVD set from Critics Choice Video. The set is, apparently, authorized by the estate of Brian Donlevy, the series' star. DeepDiscountDVD.com has the set for just $13.50 shipped. Oldies.com has plenty of classic and vintage television releases. I've purchased quite a few of their DVDs; audio/visual quality varies from series to series, depending on the source material used. They offer quite a few rare (for DVD) series that you don't see elsewhere.