(CNN) -- Serialized storytelling was around since long before daytime dramas starting selling soap.
Bill (Daniel Cosgrove) makes Lizzie (Marcy Rylan) laugh on a recent episode of "Guiding Light."
Novels used to be released in serial form, with magazines putting out chapters on a regular basis. Some caused great stirs: In a much-repeated tale, crowds of people waited on the New York docks in 1841 to greet the final chapter of Charles Dickens' "The Old Curiosity Shop," with cries of "Is Little Nell dead?" piercing the air.
In the early 20th century, the movies made hay with their own serials, such as "The Perils of Pauline" and "The Exploits of Elaine."
Modern daytime dramas have their roots in the 1930s, observes Sam Ford, an analyst with the communications firm Peppercom. He taught a course on soaps at MIT and has a forthcoming book on the subject. Gallery: Stars who started in soaps
After catching on as local Chicago programming, the shows hit the national stage, largely thanks to Irna Phillips, a writer and creator of several daytime dramas (including "Guiding Light," which is leaving the air Friday).
Phillips recognized the need for sponsors, and several brands -- particularly the detergent company Procter & Gamble -- saw a ready-made market of women.
The two quickly came together. "By the late '30s, this was a very recognizable genre," says Ford. "There were dozens of soap operas."
But it took television to bring the genre to its biggest audience. At its peak in 1963-64, the leading soap opera -- "As the World Turns," which dominated ratings for 20 years -- attracted 15.4 percent of TV households, more than 10 million viewers; four other soaps drew double-digit rating percentages as well.
"They were reliable cash cows," says Ford. "They funded the expansion of prime time."
By comparison, today's leading soap, "The Young and the Restless," did a 4.0 last season, fewer than 5 million viewers. "Guiding Light," in last place, was at 1.8.