From this morning's Robert Feder column...
Today marks the 70th anniversary of the first Chicago Cubs baseball broadcast on WGN-Channel 9. The Tribune Broadcasting station will celebrate by featuring classic Cubs memories and moments throughout tonight’s coverage of the Cubs vs. St. Louis Cardinals game, starting with the “Leadoff Man” pregame show at 5:30 p.m. “There is no relationship in TV sports we are aware of that compares to this partnership,” Bob Vorwald, executive producer and director of production at WGN, told the Tribune. “We broadcast more games over the air than all other teams combined.”
It's the 70th anniversary on WGN, but the Cubs were on TV two years earlier. Here's the description from Just One Bad Century...
April 20,1946
The first televised Cubs game airs. WBKB-TV broadcasts that first game with famous bowling announcer Whispering Joe Wilson (photo) behind the microphone. It’s a memorable day at the ballpark for a few other reasons too. It’s the 30th anniversary of the Cubs playing in Wrigley Field, and the National League Pennant is raised up the flagpole for the fifth time since the Cubs started playing there. As everyone who follows Cubs lore knows, it’s also the last time that happened until 2017. In addition, this game marks the first game back at Wrigley Field for returning soldiers Stan Musial and Enos Slaughter. Slaughter knocks in Musial for the only run the Cardinals would need that day, as the Cardinals beat star Cubs pitcher Hank Borowy. The defending NL champs will finish in 3rd place that year, 14 1/2 games out of first; a finish that wouldn’t be topped for another 20 years.