Why did GM start selling Sparks in Maryland and then pull the plug on them for the Bolt?
Well, they didn't pull the plug just for MD....all Spark EV production was ended when the Bolt was launched.
As to why GM brought them east to MD? I think the official reason was that the existing charging network was sufficient to support the Spark EV, and with DC being a big commuter area, the Spark EV fit the bill I guess.
I believe the Spark EV motor was also built in White Marsh, MD, so that might have been another factor.