Smartphones are taking over the U.S., says Nielsen research. Photo courtesy of Nielsen

If your last cellphone purchase wasn’t a smartphone and you’re living stateside, consider yourself in the minority.

So says the most recent data from Nielsen, which claims 55 percent of U.S. mobile phone purchases over the last three months were smartphones. That’s up 34 percent from last year.

“With more compelling features and lower prices, Apple’s iPhone set the trend,” said Gartner mobile analyst Ken Dulaney in an interview.

Even outside of the national market, smartphones have risen drastically since the iPhone’s debut, four years ago Wednesday. The company sold a record 18.6 million iPhones in the first three months of 2011 alone. The proliferation of new smartphone models running on the Android platform has also driven this growth: A recent tweet from Android head honcho Andy Rubin claims 500,000 daily Android device activations.

As the rise of the smartphone gradually edges out the traditional feature phone, the mobile landscape as a whole is changing dramatically. Carrying an ‘always on,’ web-connected device is slowly becoming the norm; 38 percent of U.S. mobile phone users now own smartphones. Mobile carriers saw this coming a mile away, preemptively ending unlimited data plans as smartphone data consumption rose. Like it or not, the future is mobile, web-connected and data-hungry.

“The vast majority of mobile consumers — 55 percent — are now choosing smartphones over feature phones when they purchase a new device,” a Nielsen spokesperson told Wired.com. “And they are choosing app and media-friendly devices like iPhones and Android phones.”

Interestingly enough, Android is losing some of the momentum it once had in the smartphone market. While it rose in marketshare by 20 percent over a one-year period from February 2010-11, that growth seems to have stagnated, settling around 27 percent of recent smartphone purchases over the past four months. It is, however, still the leader in terms of smartphone platform share.

Android’s growth has most likely been stymied by a surge of iPhone purchases, according to Nielsen’s data. Over the same four-month period, recent iPhone purchases jumped from 10 to 17 percent. This was probably driven by the release of the iPhone 4 on Verizon’s 3G network on Feb. 10, which allowed a flood of new customers who weren’t thrilled about AT&T’s service to buy Apple’s phone. Previous to the release, AT&T carried Apple’s phones exclusively.

Those of you who love Apple’s hardware but not the high prices may be in luck — circulating rumors suggest Apple may come out with two new phone models this fall, including a “feature phone” version of the iPhone 4, nee the iPhone 4S. However, we’re skeptical about that claim.

Android's stagnation is Apple's gain and RIM's loss, according to Nielsen data. (Photo courtesy Nielsen.)