From Wikitravel

Using abbreviations to symbolize long words or commonly known titles is encouraged. However the abbreviations used should be uniform.

[edit] Country abbreviations

Some country abbreviations include periods while others do not.

[edit] Include periods

• United States of America - should be abbreviated as U.S. with periods, not U.S.A. or US.

[edit] Exclude periods

• United Kingdom of Great Britain and Northern Ireland - should be abbreviated as UK without periods, not U.K. or GB.

[edit] Streets and Roads

• Street is St.
• Drive is Dr.
• Court is Ct.
• Road is Rd.
• Boulevard is Blvd.