Customer Geography

Our company provides mobile health testing to 1500 clients in 23 states. The testing is required once annually so we use a google spreadsheet organized by Month. this reminds us that it is time to schedule ABC company. So we have a "Scheduled Jan, Unscheduled Jan, Scheduled Feb, Unscheduled Feb and so on. I would like to be able to organize the clients by geographic proximity. This would help our scheduler plan testing weeks that are very efficient travel wise. I am thinking some kind of Geo code or similar could be added as another column in the spreadsheet after address/City/State ???