Read from Chapter 4, "1908: The Year of the Song", in Take Me Out to the Ball Game: The Story of the Sensational Baseball Song by Amy Whorf McGuiggan:

"That magical 1908 season seemed to have turned every New Yorker into a Giants—and baseball—fan. The old wooden grandstand was routinely filled with celebrities, politicians, and the stars of Broadway and vaudeville. But the thrills of that 1908 season, its ecstasies and agonies, were all still months away on the April day when Jack Norworth, riding the New York subway, saw a gaudy, lithographed poster of a silk-hosed baseball player standing with a bat on his shoulder.

Although he had never been to a professional baseball game, Norworth began to write lyrics for a baseball song, and by the time he reached his destination thirty minutes later, he had penned a song about a baseball-mad girl named Katie Casey. Conceived as a romantic ballad, the song tells the story of how, when Katie’s beau asks her to go to a show (vaudeville, no doubt), she, in her Gibson girl manner, asks instead to be taken out to the ball game.

Years after writing the song, Norworth was asked how he knew about baseball if he had never seen a professional game. He said he had listened and gotten the feel of baseball by watching bush (i.e., sandlot) games as a kid. Asked why he had decided to write a baseball song, he said that it was “simply time for a baseball song.” Norworth was, after all, a songwriter whose work, like that of all Tin Pan Alley tunesmiths, was market driven. And in 1908 few things were driving the market like baseball.

"The reign of bat and ball," noted one New York Times sports reporter, "is supreme.""