Going back to 1954, Baltimore was at the time Senators' "territory" and the rights back then were bought much cheaper. Baltimore's part-owner, Hoffberger, who was President of Natty Boh beer, agreed to pay for radio and TV advertising in the DC area. When the Senators left in '71, MLB officially ceded their area to Baltimore. The 90/10 split was the deal MLB agreed to when moving the Nats into what was Baltimore "territory" at the time Angelos bought the team in 1993. The split increases 1%/year, with the Nationals maxing out at 33%. Today, they're around 18%. Reportedly, Angelos has tried to settle the MASN business offering the Nationals almost their 33% now but it has been turned down a few times. Given the MASN arrangement, until it is dissolved, the Nationals are bound to broadcast on that network.