Major League Baseball's first night game was in 1935 in Cincinnati's Crosley Field. By 1950, 15 of the 16 franchises were playing night games. The Chicago Cubs actually intended to be one of the pioneer's of night baseball, but the outbreak of WW II sent their lighting equipment elsewhere.
So they waited, and what seemed innovative in 1940 just didn't seem right for Wrigley until August 8, 1988, when the Cubs finally turned on the lights and played ball. At least until the rain arrived.
Outside of Chicago, night baseball fundamentally changed the game. as late as the 1970s, baseball's marquee events (World Series, All-Star games) were played under the sun. Night baseball opened the sport to millions of fans who could now attend a game without taking the day off or watch from the comfort of their own couches instead of having to sneak off to the appliance store to catch a few innings of Gibson versus McLain.
Night baseball has its drawbacks. Playoff games routinely end near midnight in the Eastern Time zone, too late for kids on a school night or adults who have to punch the clock in the morning. Fans tend to leave early, and not just in Los Angeles. And it probably contributes to the "East Coast" bias of the baseball media—when West Coast night games start, much of the country is heading off to bed.
Statistically, there's not much difference between day and night baseball. Contrary to the common belief, scoring is essentially the same. For the fan, however, the feel is different. Night games, especially those during the week, are rushed affairs. Get off of work, fight traffic to the game, eat there or speed through dinner somewhere close to the park, down a couple of beers before last call and by 9:30, it's time to think about the commute home, getting ready for the following day.
And that's if there's no rain delay.
Day games are more relaxed and time is rarely the issue. If it's the weekend, you've got your free evening ahead of you, if it's during the week, well, is there anything better than playing hooky at the ballpark?
Thanks to a mix of travel logistics and nostalgia, day baseball is not dead. Teams average about 50 day games a year, mostly on weekends (outside of the Cubs), but there are get-away day games and the occasional businessman's special. Despite its infrequency, if you asked most fans to picture their perfect baseball game, it would take place during the day.
Night baseball ultimately is good for the bottom line, too. Although the game's attendance is at an all-time high, it wasn't always that way. Mid-week day game crowds used to be small (Wrigley would often do just 20,000, even in rare winning years). And there's no doubt that night games mean larger TV ratings, which means fans who see Wrigley or other parks on TV are more likely to attend in a game in the future.
As for the Cubs, their reliance on day baseball has had a number of effects. The famous collapse of 1969 was partly the result of the team being out in the hot August sun too long. In fact, five times in the 1970s the Cubs were in first place in June, only to find themselves wilting as the dog days of summer dragged on. From 1969 to 1980, the Cubs had a .516 winning percentage before the All-Star break, and a .450 percentage afterwards. In their storied 100 years of loserdom, the closest they've come to a World Series win was in 1929 when they blew an 8-run lead against the A's.
The key play: outfielder Hack Wilson lost a flyball in the sun.