Four years have been spent analyzing infant health data for Baton Rouge. As with working with any dataset, one gets a feel for the data. One such feeling was that the population being studied was mobile. The first indication came when trying to categorize the different neighborhoods in which Healthy Start program participants lived. The main reason for performing such an analysis was to gain an insight into any program participant entering the Healthy Start program, both in terms of her own previous birth outcomes and those of the neighborhood in which she lived (this will be revisited in the chapter on the Baton Rouge Healthy Start). In order to do this, one requirement was to trace pregnancy histories. As the birth and death certificate data did not come with unique identifiers, an alternative common field between birth certificates was needed. Originally, it was thought that a combination of street address, mother’s date of birth, and the date of birth of the previous child would suffice. It soon became obvious that mothers living inside the five zip code region served by the Healthy Start project were mobile. A more in-depth investigation into the degree of this mobility was needed, as there could be implications both in terms of GIS analysis, and the subsequent targeting of outreach into those identified neighborhoods.