Which of these is not like the others? Slate‘s most read stories bar features two stories from yesterday, two from Wednesday, and one from…September of last year?

It’s no glitch. The 10-part series on income inequality from September, by Timothy Noah, won the 2011 Hillman Prize in the Magazine category this week. The Prize, named for New Deal architect Sidney Hillman, is awarded annually for work that demonstrates a “sense of social responsibility” and “highlights important social and economic issues.”

In a special note featured at the top of the story, Slate says they’re “delighted that the Hillman Foundation has recognized Noah’s work.”

Hillman prizes were also awarded in the Newspaper category to Brad Heath and Kevin McCoy of USA Today, Najibullah Quaraishi of Frontline/WGBH in the Broadcast category, and Dallas Morning News‘ Mona Reeder for Photojournalism.

Read Noah’s series here, and find out more about the Hillman Prize and its winners here.

Side note: Doesn’t the Hillman Foundation logo look familiar?