Normalization for postal addresses in US (address, county, city, state, zipcode)?
I deal with millions of existing international addresses.  The following design works for my project:

Address Table

AddressLine1 varchar(255)
AddressLine2 varchar(255)
City varchar(50)
PostalCode varchar(20)
State      varchar(50)
CountryID  int  (FK to Country table)


Avoid the temptation to normalize postal codes and states, unless you really do have a master list that is updated frequently.

Countries are easier to manage, so they belong in their own lookup table. Master lists can be found online readily.