Further verification that the cause of the deepest part of the recession (2008Q3 onward) was tight money causing falling NGDP. Check out this map, courtesy of Mark Thoma:
Most of the country never experienced a housing boom, much less a bust. But the entire country (minus ND) experienced rising unemployment, and declining output.
What links the rest of the country with the most hard-hit markets? NGDP growth levels, of course!