With 13.2 million unique U.S. visitors in January 2011, the Huffington Post was the ninth most popular non-financial news website visited from home and work computers in the U.S. Its new ‘sister’ site, AOL News, was the fourth most-popular with 22.1 million U.S.-based unique visitors. AOL News is AOL’s second most popular channel – behind MapQuest – and, in effect, the Huffington Post becomes AOL’s sixth most popular property just behind AOL Messenger/AIM (with 13.3 million uniques in January) and ahead of AOL Music (with 13.1 million).

AOL’s network of websites attracted 76.2 million unique U.S. visitors in January 2011, or 39 percent of all active U.S. web users. Visitors to AOL’s websites spent an average of 1 hour 58 minutes during the month, viewing 85 pages on average. Based on average visitor January figures, each Huffington Post reader adds almost 12 minutes of time and 18 pages to the AOL portfolio – a total of 155 million minutes and 237 million page views.

Although the Huffington Post had 13.2 million U.S. uniques in January, almost 10.2 million of them also visited an AOL website, thus the net effect of AOL’s acquisition is almost 3.1 million new visitors or 1.5 percent more reach into the active U.S. Internet population. There is also a strong overlap between the Huffington Post and AOL News. In January 2011, 44 percent of visitors to the Huffington Post also visited AOL News; with 27 percent of AOL News readers also visiting the Huffington Post.

It’s not just about the extra readers the acquisition brings but the type of visitor. Although the audience makeup to AOL News and the Huffington Post is broadly similar, the latter is more concentrated around certain demographic groups. For example, the Huffington Post has a higher concentration (34%) of 18-49 year old females compared to 29 pecent for AOL News. The Internet average is 27 percent.

Although the audiences to the two entities are spread similarly geographically across the U.S., it is notable that the Huffington Post is more likely to have visitors from the West Coast while AOL News tends to have a greater concentration of visitors from New England.

The Huffington Post audience also tends to be more highly-educated – 44 percent hold a bachelor or post-graduate degree, compared to 37 percent for AOL News, 31 percent across the entire AOL portfolio and 25 percent across the entire web.

A very encouraging element of Huffington Post reader behavior for AOL concerns who consumes content. Visitors from households with incomes above $150,000 account for twice the percentage of total page views consumed on Huffington Post (12%) than they account for on AOL News (7%) and across the entire Internet (6%).

Those with a bachelor’s degree account for 50 percent more of Huffington Post content (33%) compared to AOL News (24%) and the Internet average (22%). Most starkly, those with a post-grad degree account for almost three times the percentage of Huffington Post content (34%) than they average across the whole Internet and AOL News (both 12%).

The NY Times’ website drew just over 20 million unique visitors in September — a 37% increase over unique traffic to the site last September.

Meanwhile, MSNBC saw 44% year over year growth, reaching 43.2 million unique visitors in September, according to Nielsen.

Surging interest in the U.S. presidential campaign likely drove growth for several U.S. news sites in September. 

The Anchorage Daily News in Alaska cracked Nielsen’s top 30 newspaper websites ranking for the first time, following a 928% jump in unique visitors over last September.  Sudden demand for news on Republican Vice Presidential nominee and Alaska Gov. Sarah Palin in September may have driven that dramatic increase. 

Two politics-centric sites, Politico.com (+219%) and TheHuffingtonPost.com (+457%), also saw notably large year over year percentage growth in September.

Meanwhile, Boston.com’s 122% above average growth can perhaps be attributed to Autumn baseball fever in the Hub.

Overall, all but three of the top 30 online news outlets, and all but one of the top 30 newspaper websites, attracted larger online audiences in September 2008 than they did the prior September.

View the top 30 newspaper websites for September in Editor & Publisher.

View the top 30 online news outlets for September in Editor & Publisher.

Read coverage of Nielsen’s findings in the (Toronto) Globe and Mail.