A revolution of sorts started 35 years ago, on Aug. 31, 1976, when John C. Bogle launched the Vanguard 500 Index Investor (VFINX), a mutual fund that holds all the stocks in the Standard & Poor's 500 Index ($INX).

It was the first fund to let individual investors own the broad stock market rather than actively trying to beat it.

"It was a seminal event in investing," says Dan Culloton, associate director for fund analysis at Morningstar. "It introduced passive investing to retail investors and eventually started a slow and steady revolution that continues today."

In truth, that revolution started in the 1960s with the efficient-market hypothesis championed by economists Eugene Fama and Paul Samuelson and popularized by Burton Malkiel in his 1973 book, "A Random Walk Down Wall Street." That theory, which holds that stocks are rationally priced, provided the philosophical underpinnings for simply buying and holding the entire basket of publicly available stocks.

It took a while for the idea of investing in indexes to catch on. Starting in the late 1960s, William Fouse, known as the "father of indexing," and John McQuown worked at Wells Fargo to develop an index fund for large institutions. In the early 1970s, Dean LeBaron and Jeremy Grantham at Batterymarch Financial Management also pursued index investing. But Bogle's mutual fund opened the concept to the general public and focused on providing a low fee structure to prevent returns from being eaten away.

Investors didn't exactly rush to buy Bogle's fund when it became available. It opened with $11.4 million in assets ($43 million in today's dollars), well short of Bogle's goal of $150 million. Other money managers were dismissive, if not hostile. Bogle, who founded Vanguard Group in 1974, has said he heard the fund derided as Bogle's Folly "all too often from the late 1970s through the early 1990s." Others reportedly called it un-American.

"Some of the early critics of index funds said you're not trying to identify the best-performing stocks, you are aiming deliberately for mediocrity," says Robert Arnott, a former editor of The Financial Analysts Journal and the founder of Research Affiliates, an investment management firm that offers its own twist on traditional index funds. Adds Arnott: "Jack Bogle very sensibly said, 'You know, you're absolutely right, we're aiming for mediocrity -- unfortunately, that's better than most active managers.'"

Active money managers, more often than not, fail to beat the market, and many investors may not appreciate the extent to which management fees paid to those active managers wind up eroding their returns.

"There's a very strong argument that just getting the market rate of return is actually a very attractive proposition for investors," says Vanguard Chief Investment Officer Gus Sauter. "After costs, the average investor no longer gets the market rate of return; they get the market minus costs. And the marginal outperformers become underperformers after costs. A majority of investors will underperform the market rate of return because of that."

As index funds have shown their value, investors have increasingly shifted money into them. The Vanguard 500 Index Fund reached $1 billion in assets in 1987, 11 years after its launch, and ballooned from there to become the world's largest mutual fund for a time.

"The big growth really happened starting about 1995 and on for the next five years, when really large-cap stocks outperformed quite dramatically and the S&P 500 performed extraordinarily well," says Sauter.

The fund now has $105 billion in assets. Overall, Vanguard manages about $1.7 trillion in assets, with 55% of that in passive index funds.