A lot of great cars went up for auction at Pebble Beach this past weekend, but arguably, this was the most historically important of them all. It's the very first Cobra built by Carroll Shelby, which was used both as his personal car, and for magazine testing in period. In other words, this is the very car that shocked the world back in the early-1960s.

This car, chassis CSX 2000, sold for $13.75 million including auction fees at RM Sotheby's Monterey sale, reports CNN Money. Not only does that make this the most expensive Cobra by a vast margin, it's also now the most expensive American car sold at auction. Given its history, though, it's kind of a surprise it didn't sell for more.

The car arrived in the U.S. as an engine-less AC Ace in February 1962, and Shelby installed a 260 cubic inch Ford V8 within hours of picking it up. Once CSX 2000 was completed, it was sent to magazines for instrumented testing, but interestingly, it was repainted a different color for each test to trick journalists into thinking Shelby had multiple cars.

When we tested this car back in the day, we recorded a 0-60 mph time of 4.2 seconds, a quarter-mile of 13.8 seconds at 112 mph, and a top speed of 152 mph. Impressive numbers even now, they must have been mind blowing in 1962.

CSX 2000 remained in Shelby's ownership until his 2012 death, and with his family afterwards.

So yes, $13.75 million is a lot of money, but it's somewhat shocking this car didn't sell for $20 million or more. Perhaps it will next time it comes up for sale.

via Jalopnik