Midland?
I have lived in Western Washington all my life.
The Northwest is well-known to have ‘no accent’. It’s how radio and tv people learn to speak so they can get a network/national job.
http://www.gotoquiz.com/results/what_american_accent_do_you_have
“You have a Midland accent” is just another way of saying “you don’t have an accent.” You probably are from the Midland (Pennsylvania, southern Ohio, southern Indiana, southern Illinois, and Missouri) but then for all we know you could be from Florida or Charleston or one of those big southern cities like Atlanta or Dallas. You have a good voice for TV and radio.