"The boob tube hit another milestone today, 70 years old. The first commercial telecast was July 1, 1941 by WNBT the predecessor to WNBC in New York City. The first broadcast? Of course it was sports. The Phillies and Dodgers in Brooklyn. And for the 4,000 people who actually owned TV sets at the time, if they were tuned in, they saw the first commercial. It aired before the game and was for Bulova watches. The 10-second commercial cost $9.00. The rest, is history."
From Len Berman.