Ahh yes. Well if some of them are offshore then I am not sure if that would work, but ESRI's street basemap has a network embedded in it and will allow you to use the Network Analyst toolset. I think it's worth checking out, I have run this before locating multiple location distances from the airport I work at. An O/D Cost Matrix may work as well. Good Luck! OD cost matrix analysis—Help | ArcGIS Desktop -Ben
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