I see there have been some diggz on "Mercer", so I am going to throw this out there.
With Madelyn and Stanley Dunham both working full-time, the family moved to Berkeley, California, Ponca City, Oklahoma,[10] Vernon, Texas,[11] El Dorado, Kansas, Seattle, Washington and settled in Mercer Island, Washington, where Ann Dunham graduated from Mercer Island High School
https://en.wikipedia.org/wiki/Madelyn_Dunham