While there aren't many who would consider the 2000s to be the peak of the American auto industry, this is actually a pretty overlooked era when it comes to interesting and unusual performance cars from American automakers—most of which would be hard to imagine today's market.
From budget-minded to hot hatches to exotic luxury performance cars, the 2000s were full of notable machinery, and the car we are going to talk about here certainly falls into the second of those two genres— the Cadillac XLR.
Cadillac at the Turn of the Century
The 2000s were an important time for Cadillac as the brand looked to distance itself from its soft old luxury image and into an era of sophisticated, edgier vehicles like the Euro-inspired CTS sedan.
The XLR though, was unlike anything the brand had done before and was certainly one of the most ambitious projects GM undertook during this era.
Corvette Roots
The car arrived for the 2004 model year, sharing its basic platform with the legendary Chevy Corvette and being built alongside the 'Vette at GM's legendary Bowling Green plant.
Its styling, went in a much different direction than the Corvette though—becoming essentially a production version of Cadillac's 1999 Evoq concept and fully embracing the brand's angular styling of the era. All XLRs were two-seat convertibles with power retracting tops.
XLR Under the Hood
The XLR was also a big departure from the Corvette when it came to powertrain. Under the hood sat not an LS V8 but a 4.6 liter 32-valve DOHC Northstar V8. It made 320hp and 310 pound feet of torque. Like the Corvette, the XLR used a transaxle in the rear but being a luxury-oriented machine a five-speed automatic was the only gearbox choice.
So while the flagship XLR couldn't compete with the Vette when it came to raw performance or bang for the buck, it nonetheless took advantage of the Corvette's good bones to have a stylish, modern, well-performing luxury roadster that represented Cadillac's new vibe. For its efforts, the XLR was crowned 2004 North American Car of the Year. 
XLR-V
The hot rod chapter of the XLR story came in 2006 with the debut of the XLR-V for the '06 model year, joining the CTS-V and STS-V in Caddy's high performance lineup.
It once again used a Northstar V8, but this time it displaced 4.4L and had a supercharger for a total of 443hp and 414 pound feet of torque and was mated to a six-speed automatic.
Other hardware borrowed from the Corvette helped improve the XLR-V's performance, but head to head it still couldn't match up with the standard C6 Corvette let alone the Corvette Z06 - both of which cost significantly less.
XLR Competition
It's not surprising then, that XLR always struggled to find real world buyers who wanted an American luxury two-seater that was competing primarily against cars from BMW, Mercedes, Lexus and even Porsche.
All told about 15,000 XLRs were sold during its six model year run, and like so many of those aforementioned forgotten American performance cars of the 2000s, production ended right in the midst of the economic downturn in 2009.
XLR Value
These days its incredibly rare to see an XLR on the road and even more unusual to spot an XLR-V. And that's part of the reason why they are still relatively pricey on the secondhand market.
Looking around classified sites shows standard model XLRs selling for between $18,000 and $25,000 while XLR-V models in prime condition are priced as high as $50,000.
And no matter your thoughts on how successful the XLR was as a product, there's no denying the presence the car still has more than 15 years later.
Cadillac is a brand that is always trying to reinvent itself, finding success with some vehicles (Escalade, CTS-V) and much less with others (ELR hybrid). But no matter what's to come in the future, its highly unlikely Cadillac will ever build another two-seat V8-powered roaster like the XLR again.