Yes, it's landside. Kind of a feature of about half of the larger US airports, they have separate wings for separate airlines, and rather than provided connecting corridors inside the secure area, you have to do the connecting via landside. This puts a bias on staying with one airline in hub arrangements, so there's no pressure from that side. Some airports, such as PHL, CLT, BWI put everything together, so you can swap airlines without reclearing security. SFO, LAX (with a few exceptions), JFK, BOS and many others don't have internal walkways.