Washington State has many Public Utility Districts that are city owned: Seattle City Light and Tacoma Power are the largest with their own generation, transmission and distribtution. There are many small and county size PUD's. Grant County PUD and Chelan County PUD have dams on the Columbia and very cheap power.
All PUD's have access to power from the Federal dams on the Columbia. Transmission is by BPA. Some counties are looking at taking over the power system from the private utility and going the PUD route.
City of Spokane has a 17.7 MW power system with a hydro-electric dam on the Spokane River to power the city water pumps that pull water from an underground river. Excess generation is sold to the local utility.
But none of the major PUD's are isolated from the grid. Even the old isolated diesel generator system in Elk City, Idaho is now on the grid, but via a long line. (My uncle used to maintain the Cat engine and was under a lot of pressure during summer outages to power back up ASAP before the deer and elk meat in the residents' freezers spoiled).
There is one isolated system. Chelan PUD's system for the village of Stehekin on the edge of North Cascades National Park at the north end of Lake Chelan has a small hydro unit and a couple of diesel generators. Even before fuel prices went up the PUD lost $50K/year on that system. No roads, rail or power lines into the area.