Here's another look at Kenny...
Here's another look at Kenny Howard's Flathead T roadster. Many of these cars served double duty as evidence of the windsheild and headlights installed here.
In defense of the horse racing theory, one of the best R&C articles ever was Gray Baskerville's June 2001 story, "The Legend of the Car that Raced the Horse: Why the Drags are 1,320 Feet." According to that story, hot rodding pioneer Ak Miller would have told you that "the standing quarter mile became SOP thanks to an unusual race staged between a quarter-horse and Pete Henderson's Deuce highboy" in 1944.
We've even read interviews with CJ Hart, in which he acknowledges the influence of quarter-horse racing. But Leslie Long's recollections from Santa Ana suggest a more random reason. "When they finally started to have standing starts at Santa Ana, the cars had to move away from the fence (where they had previously lined up for rolling starts). The distance that was left was a quarter mile. So it was really an accident there-it just happened to be the length of the runway."
At this race in December 1951,...
At this race in December 1951, the D Class win went to Art Chrisman in this Merc Flathead roadster, which had clutch trouble before the fastest-time races.
Leslie's version is backed up by an interview with Wally Parks from Westways magazine, published by the Southern California Auto Club (which also sponsors the Wally Parks NHRA Motorsports Museum). In that interview, Parks said specifically that the quarter mile was not from horse racing, but from test runs and races at airport runways. That distance allowed room for the cars to accelerate and decelerate without running out of pavement. Publicity in Hot Rod (edited by Parks) and other magazines helped establish the quarter mile as the standard for drag racing.

Ollie Morris and Harold Dawson...

Ollie Morris and Harold Dawson raced this roadster. "Harold [right] was one of the first people to start running weird, different fuels in his car," Leslie remembers. "I don't know all the fuels he did run, but he tried all kinds of fuel. He did real well. One time, he set it up to suck pure oxygen into the carburetor. When Don Little drove Harold's car, he would say he was afraid to get into the car!"

Mickey Thompson's might have...

Mickey Thompson's might have been first, but Leslie identifies Calvin Rice's slingshot, built by Melvin Dodd, as the first successful car of this type. The idea was to put more weight behind the rear wheels to keep them from spinning. Doug Hartelt (first to build a supercharged Chrysler) built the engine. This is from May 1957, two years after Rice won the first NHRA Nationals in Great Bend, Kansas, (and finished in Perryville, Arizona). A famous photo shows Rice at the starting line in Kansas with the Hemi, but Calvin swapped in a Flathead during the event. Rain postponed that race, and when it resumed, many weeks later in Perryville, Arizona, Rice won with the Ford engine.

More than 15 years before...

More than 15 years before Don Garlits made history by positioning himself forward of the engine, rear-engined dragsters were racing at Santa Ana. One was the Rice's Auto Parts dragster, powered by a four-banger as well as a V-8, and driven by Bill Sanders.