Creating new layers using ArcPy to define Definition Query for each field value?

I am trying to set multiple definition queries for one layer based on one field using python. ie. I have a City layer with a field that holds the city name. I want a copy of the layer in an MXD with the Definition query set for each value in the City field. So essentially, I have one source layer, with a copy of the layer as many times as there are values in the City field. The query would look like this: CITY = 'Atlanta'