According to GigaOM, PBS is debuting Prohibition in advance on iOS devices to build early buzz for the documentary. HBO's Boardwalk Empire returns on September 25, and as a highly-regarded fictional account of a Prohibition-era gangster, the HBO series is likely to generate greater interest in the nonfiction PBS series.
PBS reports that it's seen a great deal of usage of its app, with 52 million streaming views in just the last month. Prohibition's airing won't be the first time the network has offered free content through its app, either; several months back, another Ken Burns documentary streamed its first episode for free via the PBS video app.
Ken Burns has built a reputation as an outstanding documentary maker -- he's even got a film effect named for him in iMovie -- so if you're at all interested in his work or the Prohibition era itself, take a look at the series on September 23.