Over the coming months in RACER magazine and on RACER.com, we're counting down to the 100th Anniversary Indianapolis 500 with a series of fascinating insights on “The Greatest Spectacle in Racing."

In conjunction with the Indianapolis Motor Speedway and its incredible collection of photography and race records, we'll be presenting a Centenary Countdown story in every RACER magazine leading up to the 100th Anniversary Indianapolis 500 on May 29, 2011. Plus, we'll be bringing you additional stories and galleries on RACER.com.

We'll be exploring the stories behind the traditions and showcasing the heroes, the groundbreaking machines and the epic races that made the Indianapolis 500 the most important race in history.

This week, we take a look at one of the Indy 500's cornerstone traditions, the 33-car starting field, and find out that fate, circumstance…and random decisions all play their part in the story.

“400 FEET SOUNDS ABOUT RIGHT”

33 starters. It's one of those carved from Indiana limestone, never-changing traditions of the Indianapolis 500, right?

Well, not exactly…

Rewind to 1911 and 40 cars started the first Indianapolis 500 – for the simple reason that 40 of the 44 that showed up at the Indianapolis Motor Speedway were able to. Of the non-starters, one had mechanical problems, another was sidelined after an accident, and two couldn't meet the track's founding partner Carl Fisher's stipulation that every competitor must, from a flying start, cover a quarter-mile of the front straightaway at an average of 75mph.

Shortly after the 1911 race, U.S. racing's rule makers at the time, the grandly named Contest Board of the American Automobile Association (AAA), devised a formula to set a track's maximum number of starters. It determined that, to avoid dangerous crowding, a track could start one car per 400ft of its length. Based on that simple, if somewhat arbitrary, calculation, the 2.5-mile Indianapolis Motor Speedway could host 33.

Thing is, going forward, Fisher had already decided to limit the “500” to just 30 cars – not that anything like that many spots were needed for the 1912 and '13 races. They started with 24 and 27 cars, respectively, thanks to a proliferation of race-bred specials putting some manufacturers off and the auto industry's growing pains leaving others with bigger things to worry about than a mere race…

In 1914, Fisher reduced the entry fee from $500 to $200, attracted 45 entries and got his 30 starters. On a roll, he adopted AAA's 33-car limit for 1915 and was rewarded with…24 starters. A year later, with World War I raging in Europe, that fell to 21 cars – the smallest Indianapolis 500 starting field ever (RIGHT, the drivers and riding mechanics are pictured before the start). Actually, make that “Indy 300,” for Fisher had decided that the public would prefer a shorter race. Thankfully, it was a misguided one-off, but reflected well on the Speedway, which was seen to be “doing its bit” to conserve precious oil in a time of need.

America's entry into the war and the track's temporary transformation into a military repair facility meant no races in 1917-'18. But, in 1919, thanks to an entry swelled by visitors deprived of racing in battered, post-war Europe, 33 cars finally filled the field (LEFT, the pace car leads the field away at the start of the pace lap). Not that it started a trend. In fact, it wasn't until 1927 and '29 that the magic number would be reached again.

While the field fluctuated through the '20s, one innovation Fisher brought in for 1921 has remained untouched since: starting the cars in rows of three. For the first Indy 500, he'd settled on rows of five for the rolling start, switched to four-abreast for subsequent races, then finally decided that rows of three were a wiser option for the scramble into the first turn.

In November 1927, World War I fighter ace Eddie Rickenbacker (RIGHT) purchased the track as part of his growing automobiles-to-aviation empire. The Medal of Honor recipient had big ideas to revitalize the facility and the Indy 500, but hadn't counted on the Great Depression showing up.

By 1930, with the economy worsening and a ragbag mix of aging machinery and home-built specials replacing the factory entries, Rickenbacker figured anybody who'd made the effort to show up deserved every chance to race and increased the starting field to 40.

For 1933, despite the recession reaching new depths, 72 entries poured in and he upped it again, to 42 (those extra two cars got rid of an untidy, single-car final row). It remains Indy's biggest entry and starting field, but resulted in an accident-filled month of competition.

Wisely, Rickenbacker switched back to 33 for 1934 and that's how it's stayed…apart from 1947, 1979 and 1997, that is.

Next week: What happened in those years? Check out RACER.com same time next week and all will be revealed.

• For tickets to the 100th Anniversary Indianapolis 500 on May 29, 2011, CLICK HERE.

For more insight on the history and heritage of the Indianapolis 500, check out legendary Indianapolis Motor Speedway historian Donald Davidson's blog HERE on Indianapolismotorspeedway.com.

To get up close to racing history, visit the Indianapolis Motor Speedway's Hall of Fame Museum. Find out more HERE.

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