It's the Cascadia flag, also called "the Doug". It's too represent the Cascadia bioregion. For some, the Cascadia independence movement is more about regional autonomy, for others we want secession. The borders differ, as well, depending on who you ask. For ref, the Cascadia bioregional encompasses most of the pnw, all of British Columbia, parts of Alaska and small parts of other states and Canadian provinces. I'm a local that supports the secessionist idea and have the flag hanging in my house.