Screenshot by Donna Tam/CNET

Mobile is key for any organization that wants to capture the attention of Americans -- even for an institution that seems as antiquated as the public library system.

The number of Americans using mobile devices to access library Web sites has more than doubled in the last three years, according to a Pew Research Center report released today.

Based on a survey of 2,300 people in October and November, Pew determined that 13 percent of Americans ages 16 and older go to a library Web site using a mobile device. That's substantially more than the meager number of people who used mobile devices to view library sites three years ago. A survey conducted in 2009 found that 6 percent of Americans had contributed to library mobile traffic.

While a good chunk of Americans still own, and use, their library cards to borrow materials, the Pew study shows that only 25 percent of Americans ages 16 or older visited a library Web site in the last year. Most visitors -- 82 percent -- searched the site's catalog for materials. (This includes audio books, e-books, CDs, and DVDs.)

Other popular library services accessed included:

 72 percent looked for basic information like hours of operation, branch location, or directions;

 62 percent reserved materials;

 51 percent, particularly members aged 30 to 40 and those with young children, renewed materials;

 51 percent, particularly members aged 18 to 29, used an online database.