Standard Industrial Classification (SIC) codes are no longer actively being assigned, but are still in use by some publishers. Beginning in 1997, the federal government switched coding systems and is now classifying manufacturing and service industries with a North American Industrial Classification System (NAICS) code in order to promote the comparability of statistics. NAICS codes are more closely aligned with international codes. The SIC/NAICS codes are used in many online and print resources to classify establishments in the same industry. These codes can be very helpful in doing industry research.
One thing to keep in mind: the SIC code has been revised over the years and some code numbers have changed. It is important to be careful when comparing data from different publishers and over a long period of time.
We have the NAICS/SIC code manual at the Jerome Library Research & Information Desk: http://maurice.bgsu.edu/record=b2234773
Check out the Security and Exchange Commission's (SEC) website for more information: http://www.sec.gov/info/edgar/siccodes.htm
OSHA, at the United States Department of Labor, has an SIC look-up and a link to the SIC Manual: http://www.osha.gov/pls/imis/sicsearch.html
The Unitied States Census Bureau has put together a comprehensive page on NAICS codes: http://www.census.gov/epcd/www/naics.html
The United States Census Bureau also has a page comparing SIC codes to NAICS codes where you can find whichever code you have and translate it into its equivalent in the opposite classification system: http://www.census.gov/epcd/ec97brdg/