My hair is nearly black and my eyes are nearly black. There's quite a mix of hair color in people here. I'm not sure genetically why my hair and eyes are this color. Apparently my nose is a Native American feature, but I don't know which side of that family that is from.
My mother was blond as a child, and her hair turned brown as she got older. It's brown now. Sometimes you hair gets darker as you get older. Mine has always pretty much been this color, though.
I'm not sure any city has a majority of women with dark hair. Some die theirs blond also. I read that something like 1/3 of women in the U.S. are blond, while only 1/8 are naturally blond.
Me and my sis at a relative's wedding
http://i233.photobucket.com/albums/e...wedding366.jpg
If you're looking for a city with a high percentage of brunettes, it sounds like you're looking for a city with a large Italian and Hispanic and African American population.