Article · Wikipedia archive · Last revised Jun 14, 2026

Smithsonian trinomial

A Smithsonian trinomial is a unique identifier assigned to archaeological sites in many states in the United States. Trinomials are composed of a one or two digit coding for the state, typically two letters coding for the county or county-equivalent within the state, and one or more sequential digits representing the order in which the site was listed in that county. The Smithsonian Institution developed the site number system in the 1930s and 1940s, but it no longer maintains the system. Trinomials are now assigned by the individual states. The 48 states then in the union were assigned numbers in alphabetical order. Alaska was assigned number 49 and Hawaii was assigned number 50, after those states were admitted to the union. There is no Smithsonian trinomial number assigned for the District of Columbia or any United States territory.

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A Smithsonian trinomial (formally the Smithsonian Institution Trinomial System, abbreviated SITS)12 is a unique identifier assigned to archaeological sites in many states in the United States. Trinomials are composed of a one or two digit coding for the state, typically two letters coding for the county or county-equivalent within the state, and one or more sequential digits representing the order in which the site was listed in that county.34 The Smithsonian Institution developed the site number system in the 1930s and 1940s, but it no longer maintains the system. Trinomials are now assigned by the individual states. The 48 states then in the union were assigned numbers in alphabetical order. Alaska was assigned number 49 and Hawaii was assigned number 50, after those states were admitted to the union. There is no Smithsonian trinomial number assigned for the District of Columbia or any United States territory.56

Most states use trinomials of the form "nnAAnnnn", but some specify a space or dash between parts of the identifier, i.e., "nn AA nnnn" or "nn-AA-nnnn". Some states use variations of the trinomial system. Arizona, California, Connecticut, Maine, Rhode Island, and Vermont use two-letter abbreviations of the state name instead of the Smithsonian number. Alaska uses three-letter abbreviations for USGS map quadrangles in place of the county code. Arizona uses a five-part identifier based on USGS maps, specifying quadrangles, then rectangles within a quadrangle, a sequential number within the rectangle, and a code identifying the agency issuing the sequential number. California uses a three-letter abbreviation for counties. Connecticut and Rhode Island do not use any sub-state codes, with site identifiers consisting of the state abbreviation and a sequential number series for the whole state. Delaware uses a single letter code for counties and adds a block code (A-K) within each county, with sequential numbers for each block. Hawaii uses a four-part identifier, "50" for the state, a two-digit code for the island, then a two-digit code to designate the USGS topographical quad, plus a four digit sequential site number for sites on each island.

Archaeological site identification codes used by states

State Format County or equivalent codes
Alabama 1AAnnnn7 AA: The code for a county is the first two letters in the county's name, with the following exceptions: Barbour=Br, Bibb=Bb, Blount=Bt, Bullock=Bk, Cherokee=Ce, Clinton=Cn, Choctaw=Cw, Clarke=Ck, Clay=Cy, Cleburne=Cb, Colbert=Ct, Conecuh=Cc, Coosa=Cs, Dallas=Ds, DeKalb=Dk, Elmore=Ee, Lamar=Lr, Lauderdale=Lu, Macon=Mc, Maringo=Mo, Marion=My, Marshall=Ms, Mobile=Mb, Monroe=Mn, Montgomery=Mt, Morgan=Mg, St. Clair=Sc, Tallapoosa=Tp, Washington=Wn, and Wilcox=Wx.8
Alaska 49‑AAA‑nnnn9 AAA: Three letter codes are abbreviations of the names for quadrangles on USGS maps for Alaska.10
Arizona AZ AA:NN:nn(XXX)11 AA: One or two letter code, A through FF, identifying USGS map quadrangles (one degree of latitude by one degree of longitude) in Arizona.

NN: One or two digit number, 1 though 16, identifying rectangles (15' USGS maps) in a quadrangle map.12

Arkansas 3AAnnnn List of counties in Arkansas
California CA‑AAA‑nnnn13 AAA: County Abbreviation Codes (Appendix 1)
Colorado 5AAnnnn14 AA: County Abbreviation Codes
Connecticut CT‑nnnnn No county code; state abbreviation and a sequential number only
Delaware 7ABnnnn15 A: K = Kent County, N = New Castle County, and S = Sussex County. B: Figure 25: Map of blocks
Florida 8AAnnnn16 AA: The code for a county is the first two letters in the county's name, with the following exceptions: Bay=BY, Bradford=BF, Broward=BD, Collier=CR, Gadsden=GD, Hardee=HR, Hendry=HN, Highlands=HG, Lafayette=LF, Lee=LL, Levy=LV, Madison=MD, Marion=MR, Martin=MT, Miami-Dade=DA, Okeechobee=OB, Palm Beach=PB, St. Johns=SJ, St. Lucie=SL, Santa Rosa=SR, Sarasota=SO, Sumter=SM, Walton=WL, and Washington=WS.17
Georgia 9AAnnnn18 AA: County Abbreviation Codes
Hawaii 50‑AA‑BB‑nnnn19 AA: 10 = Hawaii, 20 = Kaho'olawi, 30 = Kaua'i, 40 = Lana'i, 50 = Maui, 60 = Moloka'i, 80 = O'ahu, 91 = Necker, 92 = Nihoa20
BB: USGS Quad number
Idaho 10AAnnnn AA: Idaho County Abbreviations for Site Designation
Illinois 11AAnnnn21 List of counties in Illinois
Indiana 12AAnnnn21 List of counties in Indiana
Iowa 13AAnnnn22 AA: Iowa County Abbreviations for Site Designation
Kansas 14AAnnnn23 AA: Kansas County Abbreviations for Archeological Trinomials
Kentucky 15AAnnnn21 List of counties in Kentucky ADAIR (AD); ALLEN (AL); ANDERSON (AN); BALLARD (BA); BARREN (BN); BATH (BH); BELL (BL); BOONE (BE); BOURBON (BB); BOYD (BD); BOYLE (BO); BRACKEN (BK); BREATHITT (BR); BRECKINRIDGE (BC); BULLITT (BU); BUTLER (BT); CALDWELL (CA); CALLOWAY (CW); CAMPBELL (CP); CARLISLE (CE); CARROLL (CL); CARTER (CR); CASEY (CS); CHRISTIAN (CH); CLARK (CK); CLAY (CY); CLINTON (CT); CRITTENDEN (CN); CUMBERLAND (CU); DAVIESS (DA); EDMONSON (ED); ELLIOTT (EL); ESTILL (ES); FAYETTE (FA); FLEMING (FL); FLOYD (FD); FRANKLIN (FR); FULTON (FU); GALLATIN (GA); GARRARD (GD); GRANT (GR); GRAVES (GV); GRAYSON (GY); GREEN (GN); GREENUP (GP); HANCOCK (HA); HARDIN (HD); HARLAN (HL); HARRISON (HR); HART (HT); HENDERSON (HE); HENRY (HY); HICKMAN (HI); HOPKINS (HK); JACKSON (JA); JEFFERSON (JF); JESSAMINE (JS); JOHNSON (JO); KENTON (KE); KNOTT (KT); KNOX (KX); LARUE (LU); LAUREL (LL); LAWRENCE (LA); LEE (LE); LESLIE (LS); LETCHER (LR); LEWIS (LW); LINCOLN (LI); LIVINGSTON (LV); LOGAN (LO); LYON (LY); MCCRACKEN (MCN); MCCREARY (MCY); MCLEAN (MCL); MADISON (MA); MAGOFFIN (MG); MARION (MN); MARSHALL (ML); MARTIN (MT); MASON (MS); MEADE (MD); MENIFEE (MF); MERCER (ME); METCALFE (MC); MONROE (MR); MONTGOMERY (MM); MORGAN (MO); MUHLENBERG (MU); NELSON (NE); NICHOLAS (NI); OHIO (OH); OLDHAM (OL); OWEN (ON); OWSLEY (OW); PENDLETON (PD); PERRY (PE); PIKE (PI); POWELL (PO); PULASKI (PU); ROBERTSON (RB); ROCKCASTLE (RK); ROWAN (RO); RUSSELL (RU); SCOTT (SC); SHELBY (SH); SIMPSON (SI); SPENCER (SP); TAYLOR (TA); TODD (TO); TRIGG (TR); TRIMBLE (TM); UNION (UN); WARREN (WA); WASHINGTON (WS); WAYNE (WN); WEBSTER (WE); WHITLEY (WH); WOLFE (WO); WOODFORD (WD)
Louisiana 16AAnnnn24 List of parishes in Louisiana
Maine ME-nn-nn
Maryland 18AAnnnn25 List of counties in Maryland
Massachusetts 19-AA-nnnn
Michigan 20AAnnnn26 List of counties in Michigan
Minnesota 21AAnnnn27 AA: Trinomial Site Designations for MN Counties
Mississippi 22‑AA‑nnnn28 List of counties in Mississippi
Missouri 23AAnnnn List of counties in Missouri
Montana 24AAnnnn29 AA: Trinomial Site Designations for MT Counties
Nebraska 25AAnnnn30
Nevada 26AAnnnn31
New Hampshire 27‑AA‑nnnn32 AA: Belknap (BK) · Carroll (CA) · Cheshire (CH) · Coos (CO) · Grafton (GR) · Hillsborough (HB) · Merrimack (MR) · Rockingham (RK) · Strafford (ST) · Sullivan (SU)
New Jersey 28AAnnnn
New Mexico 29AAnnnn
New York AAAAA.nnnnnn First five digits are the Minor Civil Division, followed by a sequential number for sites within that division.
North Carolina33 31AAnnnn List of counties in North Carolina

AA: Alamance (AM) · Alexander (AX) · Alleghany (AL) · Anson (AN) · Ashe (AH) · Avery (Av) · Beaufort (BF) · Bertie (BR) · Bladen (BL) · Brunswick (BW) · Buncombe (BN) · Burke (BK) · Cabarrus (CA) · Caldwell (CW) · Camden (CM) · Carteret (CR) · Caswell (CS) · Catawba (CT) · Chatham (CH) · Cherokee (CE) · Chowan (CO) · Clay (CY) · Cleveland (CL) · Columbus (CB) · Craven (CV) · Cumberland (CD) · Currituck (CK) · Dare (DR) · Davidson (DV) · Davie (DE) · Duplin (DP) · Durham (DH) · Edgecombe (ED) · Forsyth (FY) · Franklin (FK) · Gaston (GS) · Gates (GA) · Graham (GH) · Granville (GV) · Greene (GR) · Guilford (GF) · Halifax (HX) · Harnett (HT) · Haywood (HW) · Henderson (HN) · Hertford (HF) · Hoke (HK) · Hyde (HY) · Iredell (ID) · Jackson (JK) · Johnston (JT) · Jones (JN) · Lee (LE) · Lenoir (LR) · Lincoln (LN) · Macon (MA) · Madison (MD) · Martin (MT) · McDowell (MC) · Mecklenburg (MK) · Mitchell (ML) · Montgomery (MG) · Moore (MR) · Nash (NS) · New Hanover (NH) · Northampton (NP) · Onslow (ON) · Orange (OR) · Pamlico (PM) · Pasquotank (PK) · Pender (PD) · Perquimans (PQ) · Person (PR) · Pitt (PT) · Polk (PL) · Randolph (RD) · Richmond (RH) · Robeson (RB) · Rockingham (RK) · Rowan (RW) · Rutherford (RF) · Sampson (SP) · Scotland (SC) · Stanly (ST) · Stokes (SK) · Surry (SR) · Swain (SW) · Transylvania (TV) · Tyrrell (TY) · Union (UN) · Vance (VN) · Wake (WA) · Warren (WR) · Washington (WH) · Watauga (WT) · Wayne (WY) · Wilkes (WK) · Wilson (WL) · Yadkin (YD) · Yancey (YC)

North Dakota 32AAnnnn34 AA: NDCRS Site Form Training Manual - Section I: Site Identification - County Codes (Page 10)
Ohio 33‑AA‑nnnn35 AA: Appendix B: County Codes (OAI Codes) (Page 61)
Oklahoma 34AAnnnn36 AA: Table 1
Oregon37 35‑AA‑nnnn List of counties in Oregon
Pennsylvania38 36‑AA‑nnnn List of counties in Pennsylvania
Rhode Island RI‑nnnn No county code; state abbreviation and a sequential number only
South Carolina 38AAnnnn39 List of counties in South Carolina

AA: Abbeville (AB) · Aiken (AK) · Allendale (AL) · Anderson (AN) · Bamberg (BA) · Barnwell (BR) · Beaufort (BU) · Berkeley (BK) · Calhoun (CL) · Charleston (CH) · Cherokee (CK) · Chester (CS) · Chesterfield (CT) · Clarendon (CR) · Colleton (CN) · Darlington (DA) · Dillon (DN) · Dorchester (DR) · Edgefield (ED) · Fairfield (FA) · Florence (FL) · Georgetown (GE) · Greenville (GV) · Greenwood (GN) · Hampton (HA) · Horry (HR) · Jasper (JA) · Kershaw (KE) · Lancaster (LA) · Laurens (LU) · Lee (LE) · Lexington (LX) · Marion (MA) · Marlboro (ML) · McCormick (MC) · Newberry (NB) · Oconee (OC) · Orangeburg (OR) · Pickens (PK) · Richland (RD) · Saluda (SA) · Spartanburg (SP) · Sumter (SU) · Union (UN) · Williamsburg (WG) · York (YK)

South Dakota 39AAnnnn40
Tennessee41 40AAnnnn AA: County Abbreviations for Archaeological Site Numbers
Texas42 41AAnnnn AA: Texas County Abbreviations
Utah43 42‑AA‑nnnn AA: List of counties in Utah (p. 3)
Vermont44 VT‑AA‑nnnn AA: Addison (AD) · Bennington (BE) · Caledonia (CA) · Chittenden (CH) · Essex (ES) · Franklin (FR) · Grand Isle (GI) · Lamoille (LA) · Orange (OR) · Orleans (OL) · Rutland (RU) · Washington (WA) · Windham (WD) · Windsor (WN)
Virginia45 44-AA-nnnn List of county and city abbreviations in Virginia
Washington46 45‑AA‑nnnn List of counties in Washington
West Virginia47 46‑AA‑nnnn List of counties in West Virginia
Wisconsin48 47‑AA‑nnnn List of counties in Wisconsin
Wyoming49 48AAnnnn List of counties in Wyoming and also YE for sites within Yellowstone National Park
References

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External links