Just over a third of American adults own a smartphone of some kind, with many preferring to use it as their primary connection to the Internet. That's according to a report from the Pew Internet Project, which the organization says is its first standalone measure of smartphone ownership and usage in the US.

Pew surveyed 2,277 US adults between April and May of this year and found that 83 percent have some kind of cell phone. From that group, 42 percent reported owning smartphones, evening out to 35 percent of all adults surveyed. The demographics of that group are hardly surprising, either: smartphones tend to be the most popular among those with a college degree and the financially "well off," and the highest rate of ownership is among those under the age of 45.

Here's another shocker: nearly half of those who are employed full time have a smartphone, while just over a quarter of those who are not employed have one. (Feeling chained to work, anyone?) Smartphone owners are also more likely than "regular" cell owners and the general population to own laptops, music players, desktop computers, tablets, and e-book readers.

What is somewhat unexpected is the fact that there's a not-insignificant percentage of survey respondents who use their devices as the primary way to get online. According to Pew, 28 percent of smartphone owners access the Internet this way most of the time, which amounts to 10 percent of all cell owners or 8 percent of all adults in the US. Mobile-only access to the Internet is nothing new in other parts of the world, but the growing availability of smartphones and the continued difficulty of getting broadband access in low-income or rural areas is undoubtedly feeding this trend in the US.

"Smartphone owners under the age of 30, non-white smartphone users, and smartphone owners with relatively low income and education levels are particularly likely to say that they mostly go online using their phones," wrote Pew, which says that nearly a third of the "mostly cell" group lacks any kind of traditional broadband Internet access. Still, the organization points out that even among those who use their smartphone as the main source of Internet access, laptop and desktop ownership is very prevalent, indicating that they're not always going online from their phones out of necessity.

Finally, no report on smartphone adoption would be complete without some market share statistics. Pew says that 15 percent of all cell owners (35 percent of smartphone owners) reported that they own an Android device. Apple and RIM are tied at 10 percent each of all cell owners (24 percent of smartphone owners), while Microsoft and Palm both claimed two percent of all cell owners, respectively.

With Android's meteoric rise in popularity throughout 2010, we can't say we're surprised to see these numbers, though Nielsen recently reported that iPhone sales were beginning to climb again at the beginning of this year. Pew does point out some demographic differences in ownership, however. More than a quarter of African-American cell owners own an Android device—roughly twice the rate for Caucasian and Latino users. And ownership of BlackBerry and iPhones are particularly high among those with the highest level of education and incomes: these people are three to four times more likely to own a BlackBerry or iPhone than those of lower income or education levels. Additionally, those who live in urban or suburban environments are twice as likely to own an iPhone compared to rural users.

Cisco recently predicted that there will be 788 million mobile-only Internet users globally by 2015 while mobile data traffic will increase by a factor of 26 between now and then. With one in 10 cell phone owners in the US already using the Internet this way, those numbers are sure to climb as smartphones become more common among regular consumers. After all, they may eventually find that they don't necessarily need a home computer anymore, as long as they can check e-mail and Facebook on their iPhone or Android device.