There's a line-drawing issue here - the DC Metro Area is a lot more diverse than Washington DC proper. On the page you linked, DC suburbs are listed under: -

There's a line-drawing issue here - the DC Metro Area is a lot more diverse than Washington DC proper. On the page you linked, DC suburbs are listed under: - Most educational-attinment diversity (#1 & #2) - Most racial & ethnic diversity (#3 & #5) - Most birthplace diversity (#1)