Annapolis has the most zip codes in Anne Arundel County Maryland – 21401, 21405, 21402, 21411, 21403, 21412 and 21404.
Glen Burnie, Hanover and Pasadena are the other post offices with more than one zip code in this county.
In Baltimore County, Baltimore Post Office has 6 zip codes – 21250, 21282, 21251, 21284, 21252 and 21285.
Lutherville Timonium and Towson are other post offices which have more than a single zip code in the county.
In Frederick County, Frederick Post Office is the only one with more than one zip code – 21701, 21704, 21702, 21705, 21703 and 21709. There are 9 zip codes in Garrett County, Maryland.