I feel the need to clarify something. "Districts" are not individual events, but rather the entire area that is districted together into the competition structure. Michigan is a district. The Pacific Northwest is a district. DC, Maryland, and Virginia comprise the FIRST Chesapeake District.
Individual competitions are simply events. Look at the nomenclature used
here. PNW has posted their schedule, with events named using this format:
"PNW District - Auburn Mountainview Event"
I can guarantee you this is consistent with at least last year's naming system as well.