Smithsonian trinomial

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