Use the abbreviations Ave., Blvd. and St. only with a numbered address: 1600 Pennsylvania Ave. Spell them out and capitalize when part of a formal street name without a number: Pennsylvania Avenue. Lowercase and spell out when used alone or with more than one street name: Massachusetts and Pennsylvania avenues.
All similar words (alley, drive, road, terrace, etc.) always are spelled out. capitalize them when part of a formal name without a number; lowercase when used alone or with two or more names.
Always use figures for an address number: 9 Morningside Circle.
Spell out and capitalize First through Ninth when used as street names: use figures with two letters for 10th and above: 7 Fifth Ave., 100 21st St.
Abbreviate compass points used to indicate directional ends of a street or quadrants of a city in a numbered address: 222 E. 42nd St., 562 W. 43rd St., 600 K St. N.W. Do not abbreviate if the number is omitted: East 42nd Street, West 43rd Street, K Street Northwest.
See highway designations.
use periods in the abbreviation P.O. for P.O. Box numbers.