According to the Chicago Stylebook, state’s names should be completely spelled out (not abbreviated) when they stand alone and preferably (with the exception of DC) when a city precedes them. For example,
- I visited South Carolina over spring break.
- I visited Myrtle Beach, South Carolina over spring break.
When states appear in bibliographies, tabular matter, lists, and mailing addresses they are usually abbreviated.
When a state name is followed by a zip code, you should always use the two-letter, no-period abbreviation (see below). The United States Postal service prefers these abbreviations. For example,
- I live at 4989 Silver Creek Rd., Rockville, IN., 59029
Chicago Style differs from AP Style state abbreviations in that Chicago Style allows these two-letter, no-period abbreviations to be used anywhere where state abbreviations are otherwise appropriate. Chicago Style attributes the use of the older forms of abbreviations to the personal preference of the writer and editor. Both of the following examples therefore are acceptable in Chicago Style:
- Grand Rapids, MI: Baker Books
- Grand Rapids, Mich.: Baker Books
Here is a listing of U.S. States and territory abbreviations in Chicago Style (note that some states and territories have traditionally not been abbreviated).
Alaska: Alaska (AK)
Alabama: Ala. (AL)
Arkansas: Ark. (AR)
American Samoa: American Samoa (AS)
Arizona: Ariz. (AZ)
California: Calif. (CA)
Colorado: Colo. (CO)
Connecticut: Conn. (CT)
District of Columbia: D.C. (DC)
Delaware: Del. (DE)
Florida: Fla. (FL)
Georgia: Ga. (GA)
Guam: Guam (GU)
Hawaii: Hawaii (HI)
Iowa: Iowa (IA)
Idaho: Idaho (ID)
Illinois: Ill. (IL)
Indiana: Ind. (IN)
Kansas: Kans. (KS)
Kentucky: Ky. (KY)
Louisiana: La. (LA)
Massachusetts: Mass. (MA)
Maryland: Md. (MD)
Maine: Maine (ME)
Michigan: Mich. (MI)
Minnesota: Minn. (MN)
Missouri: Mo. (MO)
Mississippi: Miss. (MS)
Montana: Mont. (MT)
North Carolina: N.C. (NC)
North Dakota: N.Dak. (ND)
Nebraska: Neb. or Nebr. (NE)
New Hampshire: N.H. (NH)
New Jersey: N.J. (NJ)
New Mexico: N.Mex. (NM)
Nevada: Nev. (NV)
New York: N.Y. (NY)
Ohio: Ohio (OH)
Oklahoma: Okla. (OK)
Oregon: Ore. Or Oreg. (OR)
Pennsylvania: Pa. (PA)
Puerto Rico: P.R. or Puerto Rico (PR)
Rhode Island: R.I. (RI)
South Carolina: S.C. (SC)
South Dakota: S.Dak. (SD)
Tennessee: Tenn. (TN)
Texas: Tex. (TX)
Utah: Utah (UT)
Virginia: Va. (VA)
Virgin Islands: V.I. or Virgin Islands (VI)
Vermont: Vt. (VT)
Washington: Wash. (WA)
Wisconsin: Wis. or Wisc. (WI)
West Virginia: W.Va. (WV)
Wyoming: Wyo. (WY)