In my corner of Michigan we seem to have them now while we didn't when I was a kid. Folk wisdom is that this is due to the mosquito control trucks no longer using DEET, but I have no idea if that's true. This is in a city obviously.
Also in Michigan, and my perception is the same. I don't remember seeing them at all in my area (fairly rural exurbs) growing up. Camping in Ohio and seeing them is a vivid memory of my childhood. Now, as an adult in more or less the same area (though much closer to the city), I see them all the time in my yard.