The 1950s was when doubleheader mania hit the major leagues.
Before that, doubleheaders were seen as a necessary evil, a way to make up rained-out games, or, a way to make double the revenue by playing morning and afternoon games, which the Cubs did several times in the 1920s and 1930s. Changing times made it impractical to play morning games -- the 9-to-5 common post-World War II work schedules meant that few would have been around to attend them.
But with competition from television and families starting to move to the suburbs, teams hit on the idea of doubleheaders as an enticement. "Two games for the price of one!" This was intended to increase attendance, and in general, it did; the Sunday doubleheader became a staple for about two decades. This was much easier to accomplish when the average game time was still about two hours. Two of those plus about 20 minutes in between meant you could get the whole thing done in less than five hours. Try doing that in 2013.
Anyway, the Cubs wound up playing 30 doubleheaders in 1950 -- that's 60 total games, or almost 40 percent of the schedule, played on doubleheader dates. I don't have an original 1950 schedule available, but given the Sunday/holiday doubleheader tradition of the tim, it appears that 18 of the twin bills were on the original schedule, and 12 of them were forced by rainouts. Postponements, as I have previously mentioned, were much more common in those days. A one-hour rainshower would do it, given the poor drainage conditions; so would extremely cold weather, or even sometimes just a forecast of rain.
All of this is prelude to the doubleheader played Sunday, August 27 at Wrigley Field. The Cubs lost the first game 6-1 to the pennant-bound Phillies, and then the second game went into extra innings. Edward Burns of the Tribune picks up the story, as the Phillies:
... overcame a 4 to 1 lead the Cubs had at the end of three innings and battled to a 4 to 4 tie in the second game, which was called because of darkness at the end of 11 innings. As a result of the tie, another double header will be played this afternoon. Curt Simmons and Ken Johnson are slated to pitch for the pace setters, and Dutch Leonard and Johnny Klippstein for the Cubs.
Right there is a partial explanation for why the Cubs were so bad in the 1950s. Leonard, 41 years old, was really a reliever by that time -- this was his only start of 1950. Klippstein, then a 23-year-old rookie, struggled through five mediocre seasons with the Cubs and then was traded to Cincinnati for no one you've ever heard of. He later became an effective reliever for most of the 1960s for several teams, notably the 1965 American League champion Twins.
Burns had one more note on the game:
The crowd, most of which stayed until the finish a few minutes after 7 o'clock, lifted the home attendance at Wrigley field to 1,031,895. It was the sixth successive year the Cubs have played to more than 1,000,000 at home. They had a run of five such years from 1927 to 1931.
The Cubs lost 89 games in 1950, saved from a third straight 90-loss season only by a rained-out game in Cincinnati that could not be made up. Home attendance wound up at 1,165,944, but the team would draw over one million just once between 1951 and 1968 (1952, when they finished at .500 and Hank Sauer was National League MVP).
And from the results, it would appear that was one of the primary reasons the Cubs were so bad in 1950. They simply didn't have enough depth in the pitching staff. Of the 30 doubleheaders, they swept four, split seven and were swept 18 times, in addition to this August 27 twin bill where they lost the first game and tied the second. That's a record of 15-44-1 in those games; the Cubs were 49-45 in games not played a part of a doubleheader in 1950.
Finally, why they didn't get the idea to suspend these games is beyond me. To play 11 innings, then have to start over from the beginning the next day? What sense does that make? At least they finally figured that out, though it would take almost 20 more years.